{"id":7164,"date":"2026-08-19T11:59:52","date_gmt":"2026-08-19T11:59:52","guid":{"rendered":"https:\/\/www.london-dermatology-centre.co.uk\/blog\/?p=7164"},"modified":"2026-08-25T09:06:41","modified_gmt":"2026-08-25T09:06:41","slug":"the-history-of-phototherapy","status":"publish","type":"post","link":"https:\/\/www.london-dermatology-centre.co.uk\/blog\/the-history-of-phototherapy\/","title":{"rendered":"The History of Phototherapy: The Evolution of PUVA and Narrowband UVB Treatment"},"content":{"rendered":"\n

If you have been offered phototherapy for psoriasis, eczema, vitiligo or another long-term skin condition, you may wonder how light became a medical treatment. Today, specialist dermatology units can deliver carefully measured ultraviolet light while controlling the wavelength and dose reaching your skin.<\/p>\n\n\n\n

Modern phototherapy developed through generations of research into the effects of sunlight on skin. Two major advances were PUVA, which combines psoralen with UVA, and narrowband UVB, which uses a selected part of the UVB spectrum, helping move treatment from broad light exposure to much more precise therapy.<\/p>\n\n\n\n

How Did Medical Interest in Light Begin?<\/strong><\/h2>\n\n\n\n

You do not need special equipment to notice how sunlight affects your skin. You may see your skin tan, become red or burn, and if you have a skin condition, you may also notice that your symptoms sometimes change with sun exposure.<\/p>\n\n\n\n

Doctors eventually began asking whether they could use the helpful effects of sunlight while limiting the damage. As scientists learnt more about ultraviolet radiation and developed reliable artificial light sources, you could be treated with a measured dose rather than simply being advised to spend more time in the sun.<\/p>\n\n\n\n

How Did Niels Finsen Turn Light into a Medical Treatment?<\/strong><\/h2>\n\n\n\n

One of the most important figures in medical light treatment was the Danish physician Niels Ryberg Finsen. In the 1890s, he studied how light affected the body and developed ways to concentrate particular parts of the spectrum, using concentrated light to treat lupus vulgaris, a form of tuberculosis affecting the skin.<\/p>\n\n\n\n

Finsen’s work showed that light could be used as a controlled medical treatment rather than simply relying on sunlight. Although modern phototherapy equipment looks very different from his early apparatus, the basic idea remains similar: identify useful wavelengths, control the dose reaching your skin and monitor how you respond. Finsen\u2019s work was recognised with the 1903 Nobel Prize in Physiology or Medicine for his contribution to treating disease, particularly lupus vulgaris, with concentrated light radiation.<\/p>\n\n\n\n

Why Do Different Types of UV Light Affect Your Skin Differently?<\/strong><\/h2>\n\n\n\n
\"\"<\/figure>\n\n\n\n

As scientists learnt more about how light affects your skin, they realised that ultraviolet radiation is not all the same. UVA has longer wavelengths, while UVB has shorter wavelengths and mainly affects the more superficial layers of your skin, so different wavelengths can produce different biological effects.<\/p>\n\n\n\n

This helped doctors work out which parts of ultraviolet light were actually useful for treating skin conditions. PUVA uses UVA together with a photosensitising medicine, while narrowband UVB focuses treatment on a smaller, more useful part of the UVB spectrum.<\/p>\n\n\n\n

How Did Psoralens Pave the Way for PUVA?<\/strong><\/h2>\n\n\n\n

The \u2018P\u2019 in PUVA refers to psoralen, a photosensitising medicine that makes your skin more sensitive to UVA. Researchers had been exploring this effect for years, and in 1948, Egyptian dermatologist Abdel Monem El Mofty used purified 8-methoxypsoralen to treat vitiligo, helping lay the groundwork for modern photochemotherapy.<\/p>\n\n\n\n

The basic idea was to combine psoralen with controlled ultraviolet light exposure. However, doctors still needed to understand how the combination worked and how to use it safely, leading to major advances in psoralen and UVA research during the 1960s and 1970s.<\/p>\n\n\n\n

Why Did Psoriasis Drive Phototherapy Research?<\/strong><\/h2>\n\n\n\n

Psoriasis could be difficult to control, especially when thick, inflamed and scaly areas covered large parts of your body. Before modern biologic and targeted medicines were available, doctors had fewer options, so light therapy offered a practical way to treat wider areas of skin at once.<\/p>\n\n\n\n

Researchers also began looking at how psoralens could make your skin more responsive to UVA. By combining the medicine with controlled light exposure, they created a new approach in which the psoralen and UVA worked together, leading to one of the major advances in 20th-century dermatological treatment.<\/p>\n\n\n\n

How Did PUVA Become an Important Treatment in the 1970s?<\/strong><\/h2>\n\n\n\n

The modern era of PUVA is closely linked to the work of John Parrish, Thomas Fitzpatrick, Lewis Tanenbaum and Madhukar Pathak. In 1974, they published an influential study showing that oral methoxsalen followed by long-wave UVA could effectively treat psoriasis, helping establish the approach now known as PUVA, meaning psoralen plus UVA.<\/p>\n\n\n\n

This research helped establish PUVA as an important treatment option for widespread psoriasis that could not be controlled with topical treatment alone. Larger clinical studies in the late 1970s then helped confirm its use in wider clinical practice.<\/p>\n\n\n\n

What Actually Happens During PUVA Treatment?<\/strong><\/h2>\n\n\n\n
\"\"<\/figure>\n\n\n\n

If you hear the term PUVA, remember that you are not simply receiving ultraviolet light. You first receive a psoralen to make your skin more sensitive to UVA, followed by a carefully calculated dose of UVA radiation at the appropriate time.<\/p>\n\n\n\n

Your treatment may involve oral methoxsalen or another method of giving psoralen, depending on your condition and treatment plan. Because your skin\u2019s sensitivity and response to previous sessions matter, your phototherapy team can adjust the UVA dose throughout the course, making the treatment more like a carefully measured medicine than ordinary UV exposure.<\/p>\n\n\n\n

Clinical Tip<\/strong><\/p>\n\n\n\n

If you receive oral PUVA, the precautions continue after you leave the phototherapy unit. Psoralen can make both your skin and eyes more sensitive to UVA for many hours. You must therefore wear suitable UVA-protective glasses after taking the tablets, as instructed by your phototherapy team, as well as the protective goggles provided during treatment. Follow the exact eye- and sun-protection instructions given by your phototherapy team.<\/p>\n\n\n\n

How Did PUVA Expand Beyond Psoriasis?<\/strong><\/h2>\n\n\n\n

Psoralen-based light treatment was already being explored for vitiligo before PUVA became established for psoriasis. If you have a light-responsive condition, this history helps explain why PUVA later became an option beyond psoriasis, although its suitability still depends on your diagnosis and individual risks.<\/p>\n\n\n\n

As clinical experience grew, doctors learnt that PUVA could affect inflammation, skin-cell activity and pigmentation. This expanded the conditions for which you might be considered for treatment, while research into UVB wavelengths was developing a different option that did not require psoralen.<\/p>\n\n\n\n

What Should You Know About the Limitations of PUVA?<\/strong><\/h2>\n\n\n\n

PUVA was a major advance, but as its use expanded and cumulative treatment exposure increased, its limitations became clearer. If you take oral psoralen, you become temporarily more sensitive to UVA, so you need extra precautions, and you may experience effects such as redness, itching or nausea.<\/p>\n\n\n\n

Long-term follow-up showed that PUVA is associated with an increased risk of squamous cell carcinoma, with the risk rising as the cumulative number of treatments increases. Repeated exposure can also contribute to photoageing. PUVA remains an effective treatment, but these findings encouraged doctors to look for other options, including UVB treatments that do not require a photosensitising medicine.<\/p>\n\n\n\n

Why Was Broadband UVB Less Targeted?<\/strong><\/h2>\n\n\n\n

Before narrowband UVB became established, broadband UVB was commonly used to treat psoriasis and other inflammatory skin conditions. However, it exposed your skin to a wider range of wavelengths, including some that could cause redness without adding much therapeutic benefit.<\/p>\n\n\n\n

Researchers therefore began looking more closely at which UVB wavelengths worked best for psoriasis. Instead of giving you a broad range of UVB, the aim was to identify the most useful wavelengths and design treatment around them, making phototherapy more focused and controlled.<\/p>\n\n\n\n

How Did Researchers Identify the Most Useful UVB Wavelengths?<\/strong><\/h2>\n\n\n\n

A key study by John Parrish and Kurt Jaenicke in 1981 compared individual ultraviolet wavelengths from 254 to 313 nanometres in psoriasis. Their work showed that wavelength mattered: shorter wavelengths such as 254, 280 and 290 nanometres could cause redness without producing the same useful therapeutic response, while 313 nanometres showed effective antipsoriatic activity.<\/p>\n\n\n\n

These findings showed why exposing your skin to more UVB wavelengths was not necessarily better. Focusing treatment on a more useful part of the spectrum could provide therapeutic benefit while avoiding some wavelengths that mainly caused redness. This principle later supported the development of narrowband UVB lamps centred close to 311 nanometres.<\/p>\n\n\n\n

How Did the TL-01 Lamp Make UVB Treatment More Targeted?<\/strong><\/h2>\n\n\n\n

A major step towards narrowband UVB came with the Philips TL-01 fluorescent lamp, which produced a focused emission around 311 nanometres. This meant you could receive a more selective UVB treatment, based on research showing which wavelengths were most useful for psoriasis.<\/p>\n\n\n\n

The TL-01 lamp was developed during the 1980s, and clinical studies published from the late 1980s onwards helped establish narrowband UVB as an effective treatment for psoriasis.<\/p>\n\n\n\n

Key Milestones in the History of Phototherapy<\/strong><\/h2>\n\n\n\n
Period<\/strong><\/td>Development<\/strong><\/td>Why It Mattered<\/strong><\/td><\/tr><\/thead>
1890s<\/td>Niels Finsen developed concentrated-light treatment for lupus vulgaris<\/td>Helped establish controlled light as medical therapy<\/td><\/tr>
1903<\/td>Finsen received the Nobel Prize<\/td>Recognised phototherapy as an important medical advance<\/td><\/tr>
1948<\/td>El Mofty used psoralen-based treatment for vitiligo<\/td>Helped establish modern psoralen photochemotherapy<\/td><\/tr>
1974<\/td>Parrish and colleagues reported oral methoxsalen plus UVA for psoriasis<\/td>Helped establish modern PUVA<\/td><\/tr>
Late 1970s<\/td>Larger clinical studies expanded the evidence for PUVA<\/td>Helped establish wider clinical use<\/td><\/tr>
1981<\/td>Parrish and Jaenicke studied the ultraviolet action spectrum for psoriasis<\/td>Showed why wavelength selection mattered<\/td><\/tr>
Late 1980s\u20131990s<\/td>TL-01 narrowband UVB became established<\/td>Allowed treatment centred around approximately 311 nm<\/td><\/tr>
Modern practice<\/td>NB-UVB, PUVA and other forms of phototherapy are individually dosed<\/td>Balances treatment response, convenience and cumulative UV risk<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Why Is Narrowband UVB Often Preferred Today?<\/strong><\/h2>\n\n\n\n

Narrowband UVB became attractive because you did not need to take psoralen before treatment, making the process simpler than PUVA. You could receive a carefully calculated UVB dose and leave afterwards without the prolonged photosensitivity linked to oral psoralen.<\/p>\n\n\n\n

You still need controlled dosing because too much UVB can cause redness or burns, but the narrower wavelength range allowed treatment to focus on a more therapeutically useful part of the UVB spectrum. Today, you may be offered narrowband UVB for conditions such as psoriasis, vitiligo or atopic dermatitis, depending on your condition, its severity and your individual circumstances.<\/p>\n\n\n\n

How Is Your Phototherapy Dose Personalised?<\/strong><\/h2>\n\n\n\n
\"\"<\/figure>\n\n\n\n

Modern phototherapy is not simply about standing in front of a UV lamp for a set amount of time. Your treatment dose is carefully planned around your skin sensitivity, previous exposure, the condition being treated and how you responded to your last session.<\/p>\n\n\n\n

You usually receive treatment as a course, with the dose gradually adjusted if your skin tolerates it well. Your eyes are protected, areas may be covered when needed, and your medicines are considered because some can make you more sensitive to light, showing how carefully your treatment is now controlled. Phototherapy services also keep records of your cumulative UV exposure because the number of treatments can become important when considering long-term safety.<\/p>\n\n\n\n

How Do PUVA and Narrowband UVB Compare?<\/strong><\/h2>\n\n\n\n

It may seem that narrowband UVB simply replaced PUVA, but the reality is more nuanced. With NB-UVB, you receive a focused UVB treatment without psoralen, while PUVA combines UVA with a photosensitising medicine, so each approach has different benefits.<\/p>\n\n\n\n

Your dermatologist considers your condition, how widespread it is, your previous treatment response and your individual risk factors when choosing between them. PUVA may still be useful for certain thicker or difficult-to-treat conditions, while NB-UVB is often preferred because you do not need to take a photosensitising medicine.<\/p>\n\n\n\n

UK Guidance Note<\/strong><\/p>\n\n\n\n

Narrowband UVB is often preferred as the first phototherapy option for conditions such as psoriasis because it does not require psoralen and is generally simpler to administer than PUVA. PUVA can still be useful in selected situations, particularly when narrowband UVB has not provided enough benefit or for certain difficult-to-treat conditions.<\/p>\n\n\n\n

Both treatments require careful monitoring of your response and cumulative ultraviolet exposure. PUVA has a well-established association with an increased risk of squamous cell carcinoma after substantial cumulative exposure, which is one reason your previous phototherapy history is considered when further treatment is planned.<\/p>\n\n\n\n

Where Does Phototherapy Fit into Treatment Today?<\/strong><\/h2>\n\n\n\n

Today, you have access to advanced creams, systemic medicines and biologic treatments that early phototherapy researchers could never have imagined. Even so, phototherapy can still be useful when larger areas of your skin are affected and topical treatment is difficult or systemic medicine is not suitable.<\/p>\n\n\n\n

You may also benefit from treatment that is delivered directly to your skin rather than taken as a systemic medicine. Although regular visits and careful UV monitoring are still needed, modern phototherapy remains relevant because treatment can now be delivered using carefully selected wavelengths, individually adjusted doses and structured clinical monitoring.<\/p>\n\n\n\n

Myth vs Fact<\/strong><\/h2>\n\n\n\n
Myth<\/strong><\/td>Fact<\/strong><\/td><\/tr><\/thead>
Phototherapy is the same as using a sunbed.<\/td>No. Medical phototherapy delivers selected ultraviolet wavelengths using carefully measured doses and clinical monitoring.<\/td><\/tr>
PUVA is just UVA light.<\/td>No. PUVA combines UVA with a photosensitising medicine called psoralen.<\/td><\/tr>
Narrowband UVB contains no risk because it is more targeted.<\/td>No. It can still cause redness, burning and cumulative UV exposure, so treatment is monitored.<\/td><\/tr>
Narrowband UVB completely replaced PUVA.<\/td>No. PUVA can still be useful for selected patients and conditions.<\/td><\/tr>
A stronger UV dose always works better.<\/td>No. Phototherapy doses are adjusted according to your skin response because excessive UV can cause burns and other complications.<\/td><\/tr>
Once my skin improves, I should continue maintenance phototherapy indefinitely.<\/td>Not routinely for psoriasis. Maintenance narrowband UVB or PUVA is generally avoided after a treatment course has finished, although your dermatologist will advise you based on your individual circumstances.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Frequently Asked Questions<\/strong><\/h2>\n\n\n\n

1. What is phototherapy, and how can it help you?
<\/strong>Phototherapy uses carefully controlled ultraviolet light to treat certain skin conditions. Depending on your condition, your dermatologist may recommend narrowband UVB or PUVA to reduce inflammation, slow excessive skin-cell growth or encourage repigmentation.<\/p>\n\n\n\n

2. When might you need phototherapy?
<\/strong>You may be offered phototherapy when creams and ointments are not controlling your symptoms well enough, particularly if you have widespread psoriasis, eczema, vitiligo or another condition that responds to ultraviolet light.<\/p>\n\n\n\n

3. What is the difference between PUVA and narrowband UVB?
<\/strong>PUVA combines a medicine called psoralen with UVA light, while narrowband UVB uses a focused range of UVB wavelengths, usually around 311\u2013313 nanometres. With narrowband UVB, you generally do not need to take a photosensitising medicine before treatment.<\/p>\n\n\n\n

4. How does PUVA treatment work?
<\/strong>If you have oral PUVA, you usually take prescribed psoralen before your treatment. This makes your skin more sensitive to UVA, allowing the controlled light exposure to produce therapeutic effects on skin cells and immune activity.<\/p>\n\n\n\n

5. Why is narrowband UVB commonly used today?
<\/strong>Narrowband UVB can treat widespread skin disease without the need for psoralen. Because it uses a focused part of the UVB spectrum, it can provide useful therapeutic effects while limiting exposure to wavelengths that are more likely to cause unnecessary redness and burning.<\/p>\n\n\n\n

6. Can phototherapy help you if you have vitiligo?
<\/strong>Yes. Narrowband UVB is an established treatment option for vitiligo and can help encourage repigmentation in suitable patients. Your response can vary depending on factors such as the extent and location of your vitiligo.<\/p>\n\n\n\n

7. Can phototherapy help with eczema?
<\/strong>Yes. If your eczema is widespread or has not responded sufficiently to topical treatments, your dermatologist may consider narrowband UVB or another form of phototherapy. Treatment is tailored to your skin and the type of eczema you have.<\/p>\n\n\n\n

8. Is PUVA still used today?<\/strong><\/p>\n\n\n\n

Yes. Although narrowband UVB is often preferred for many conditions, PUVA remains useful for selected patients and certain difficult-to-treat skin conditions. Your dermatologist will consider the potential benefits and risks before recommending it.<\/p>\n\n\n\n

9. Is phototherapy safe for you?
<\/strong>Phototherapy is carefully dosed and monitored, but no form of therapeutic UV exposure is completely risk-free. Both PUVA and narrowband UVB can cause redness or burning, and repeated UV exposure can contribute to photoageing. PUVA has a particularly well-established cumulative risk of squamous cell carcinoma, so your total treatment exposure is recorded and considered when further courses are planned.<\/p>\n\n\n\n

10. What happens during a modern phototherapy session?
<\/strong>You will usually receive a carefully measured dose of UV light in a specialised treatment unit. Your skin response is monitored and the dose can be adjusted from one session to the next. You may also need protective goggles or coverings for areas that should not receive UV exposure. If you are receiving oral PUVA, you will also be given specific instructions about protecting your eyes and skin from UVA after taking psoralen.<\/p>\n\n\n\n

Final Thoughts: What the History of Phototherapy Means for You<\/strong><\/h2>\n\n\n\n

Phototherapy has evolved from early sunlight-based treatments into carefully controlled PUVA and narrowband UVB therapy. If you are offered phototherapy for psoriasis, eczema, vitiligo or another suitable condition, your treatment can now use selected wavelengths and individually adjusted doses rather than uncontrolled light exposure.<\/p>\n\n\n\n

Your dermatologist can consider your diagnosis, skin response, previous UV exposure, medicines and individual risk factors when planning treatment. Although newer medicines have expanded your options, phototherapy remains relevant because it can treat larger areas of your skin while allowing the dose and cumulative exposure to be carefully monitored.<\/p>\n\n\n\n

References<\/strong><\/h2>\n\n\n\n
    \n
  1. Parrish, J.A., Fitzpatrick, T.B., Tanenbaum, L. and Pathak, M.A. (1974) \u2018Photochemotherapy of psoriasis with oral methoxsalen and longwave ultraviolet light\u2019, The New England Journal of Medicine<\/em>, 291(23), pp. 1207\u20131211. Available at: https:\/\/pubmed.ncbi.nlm.nih.gov\/4422691\/<\/a><\/li>\n\n\n\n
  2. Parrish, J.A. and Jaenicke, K.F. (1981) \u2018Action spectrum for phototherapy of psoriasis\u2019, Journal of Investigative Dermatology<\/em>, 76(5), pp. 359\u2013362. Available at: https:\/\/pubmed.ncbi.nlm.nih.gov\/7229428\/<\/a><\/li>\n\n\n\n
  3. Ibbotson, S.H. (2018) \u2018A perspective on the use of NB-UVB phototherapy vs. PUVA photochemotherapy\u2019, Frontiers in Medicine<\/em>, 5, article 184. Available at: https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC6036147\/<\/a><\/li>\n\n\n\n
  4. de Moura Barros, N. et al.<\/em> (2021) \u2018Phototherapy\u2019, Anais Brasileiros de Dermatologia<\/em>, 96(4), pp. 397\u2013407. Available at: https:\/\/www.sciencedirect.com\/science\/article\/pii\/S0365059621000805<\/a><\/li>\n\n\n\n
  5. Stern, R.S., Liebman, E.J. and V\u00e4kev\u00e4, L. (1998) \u2018Oral psoralen and ultraviolet-A light (PUVA) treatment of psoriasis and persistent risk of nonmelanoma skin cancer\u2019, Journal of the National Cancer Institute<\/em>, 90(17), pp. 1278\u20131284. Available at: https:\/\/pubmed.ncbi.nlm.nih.gov\/9731734\/<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"

    If you have been offered phototherapy for psoriasis, eczema, vitiligo or another long-term skin condition, you may wonder how light became a medical treatment. Today, specialist dermatology units can deliver carefully measured ultraviolet light while controlling the wavelength and dose reaching your skin. Modern phototherapy developed through generations of research into the effects of sunlight […]<\/p>\n","protected":false},"author":4,"featured_media":7185,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_et_pb_use_builder":"off","_et_pb_old_content":"","_et_gb_content_width":"","om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-7164","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized"],"acf":[],"aioseo_notices":[],"rttpg_featured_image_url":{"full":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95.jpg",1100,600,false],"landscape":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95.jpg",1100,600,false],"portraits":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95.jpg",1100,600,false],"thumbnail":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95-150x150.jpg",150,150,true],"medium":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95-300x164.jpg",300,164,true],"large":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95-1024x559.jpg",1024,559,true],"1536x1536":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95.jpg",1100,600,false],"2048x2048":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95.jpg",1100,600,false],"et-pb-post-main-image":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95-400x250.jpg",400,250,true],"et-pb-post-main-image-fullwidth":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95-1080x600.jpg",1080,600,true],"et-pb-portfolio-image":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95-400x284.jpg",400,284,true],"et-pb-portfolio-module-image":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95-510x382.jpg",510,382,true],"et-pb-portfolio-image-single":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95-1080x589.jpg",1080,589,true],"et-pb-gallery-module-image-portrait":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95-400x516.jpg",400,516,true],"et-pb-post-main-image-fullwidth-large":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95.jpg",1100,600,false],"et-pb-image--responsive--desktop":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95.jpg",1100,600,false],"et-pb-image--responsive--tablet":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95-980x535.jpg",980,535,true],"et-pb-image--responsive--phone":["https:\/\/www.london-dermatology-centre.co.uk\/blog\/wp-content\/uploads\/2026\/08\/1-95-480x262.jpg",480,262,true]},"rttpg_author":{"display_name":"Shailendra Kumar","author_link":"https:\/\/www.london-dermatology-centre.co.uk\/blog\/author\/shailendra\/"},"rttpg_comment":0,"rttpg_category":"Uncategorized<\/a>","rttpg_excerpt":"If you have been offered phototherapy for psoriasis, eczema, vitiligo or another long-term skin condition, you may wonder how light became a medical treatment. 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