Phototherapy
Phototherapy uses selected wavelengths of non-ionizing electromagnetic radiation to treat chronic skin diseases. Unlike natural sunlight, whose broad spectrum carries a high risk of sunburn, modern phototherapy relies on narrow wavebands with the strongest biological effect, especially narrowband UVB (NB-UVB, 311 nm) and psoralen plus UVA (PUVA).
It works by calming the local immune response, slowing runaway keratinocyte growth and stimulating repigmentation. At Haute-Derma, our full-body cabins and targeted phototherapy units are run to strict medical safety standards, with each patient's minimal erythema dose (MED) and minimal phototoxic dose (MPD) determined individually.
How Phototherapy Works
Immunosuppressive and Anti-Inflammatory Effects (Immunomodulation)
- T-cell apoptosis: NB-UVB (311 nm) passes through the epidermis into the upper dermis and creates DNA damage (cyclobutane pyrimidine dimers, CPDs) in infiltrating T lymphocytes. This triggers p53-dependent programmed cell death (apoptosis), relieving the skin of attack by autoreactive T cells.
- Suppression of the IL-23/IL-17 and Th1/Th2 cytokine axes: The 311 nm band reduces antigen presentation by Langerhans cells and dampens secretion of IL-17A, IL-22, IFN-gamma and IL-4, weakening the inflammatory cascade in psoriasis and atopic dermatitis.
- Slowing keratinocyte proliferation: Phototherapy slows the cell cycle of rapidly dividing keratinocytes and restores normal differentiation.
Stimulating Repigmentation in Vitiligo
- Activating follicular melanocytes: NB-UVB prompts surviving melanocyte stem cells in the hair follicle to multiply, migrate up into the depigmented epidermis and start producing melanin.
- A more favorable cellular environment: Reduces attack by cytotoxic CD8+ T cells on melanocytes at the edges of the patches.
Types of Clinical Phototherapy
- Narrowband UVB (NB-UVB, 311 nm):
- Features: Fluorescent lamps emitting a very narrow band peaking at 311 nm.
- Advantages: Clearly more effective than broadband UVB, with a lower risk of burning and no need for a photosensitizing drug. It is the gold standard for psoriasis, vitiligo, atopic dermatitis and parapsoriasis.
- PUVA (psoralen + UVA 320–400 nm):
- How it works: A photosensitizer, psoralen (8-methoxypsoralen, 8-MOP, taken by mouth or applied topically or as a soak), is combined with UVA exposure. Psoralen binds to cellular DNA, and when activated by UVA it forms interstrand cross-links that halt cell division.
- Indications: Thick, treatment-resistant plaque psoriasis, cutaneous T-cell lymphoma (mycosis fungoides) and mastocytosis.
- Excimer laser / excimer light (308 nm):
- Features: Delivers a 308 nm wavelength at high energy density.
- Advantages: Treats localized patches precisely while sparing the surrounding healthy skin as much as possible. Ideal for limited vitiligo and for localized psoriasis on the hands, feet or scalp.
- UVA1 (340–400 nm):
- Features: Penetrates deep into the dermis and subcutis.
- Indications: Scleroderma, mixed connective tissue disease and severe atopic dermatitis.
Phototherapy Methods: Mechanisms and Indications
| Method | Molecular / Cellular Mechanism | Main Indications |
|---|---|---|
| NB-UVB (311 nm) | T-cell apoptosis, reduced IL-17/23, melanocyte activation | Psoriasis, vitiligo, atopic dermatitis, parapsoriasis |
| Systemic PUVA | DNA cross-linking that fully blocks the cell cycle | Severe thick plaque psoriasis, mycosis fungoides |
| Excimer 308 nm | High-intensity localized T-cell apoptosis | Limited vitiligo, localized psoriasis |
| UVA1 | Induces MMP-1 to break down collagen, reduces T cells | Scleroderma, lichen sclerosus, atopic dermatitis |
Safety, Skin Cancer Risk and Contraindications
- Burning and phototherapy-induced erythema: Redness occurs when the dose exceeds what the skin can tolerate (the MED). The skin reaction is checked 12–24 hours after each session to adjust the dose increments (usually a 10–20% increase per session if there is no redness).
- Long-term skin cancer risk (carcinogenesis):
- NB-UVB: Large long-term follow-up studies show NB-UVB to be very safe, with no statistically significant rise in squamous cell carcinoma (SCC) or basal cell carcinoma (BCC) seen in East Asian patients.
- PUVA: Long-term PUVA (more than 150–200 sessions) clearly increases the risk of squamous cell carcinoma (SCC) and melanoma. The total number of PUVA sessions over a patient's lifetime must be limited.
- Eye toxicity: UV light and psoralen can accumulate in the lens of the eye. Patients must wear fully UV-blocking eye protection throughout every cabin session and for 24 hours after taking oral 8-MOP for PUVA.
- Absolute contraindications:
- Inherited photosensitivity syndromes (xeroderma pigmentosum, Bloom syndrome).
- Systemic lupus erythematosus (SLE) or photosensitive cutaneous lupus.
- A history of melanoma.
Our Treatment Process at Haute-Derma
Clinical Assessment and Minimal Erythema Dose (MED) Testing
- We determine your Fitzpatrick skin type (I–VI) and review any photosensitizing medications (tetracycline, thiazides, doxycycline).
- MED test: small squares of covered skin (such as the buttock or thigh) are exposed to increasing doses to find the lowest dose that causes clear redness after 24 hours.
Starting Treatment in the Cabin or with a Targeted Device
- Starting dose: 70% of the measured MED (or based on a standard skin-type chart).
- Protecting sensitive areas: Patients wear UV goggles, cover the genitals (with dark underwear) and shield the face if it is not affected.
- Gradual dose increases: If there is no redness after 24 hours, the next dose is raised by 10–15%. If there is mild redness, the dose stays the same. If redness persists and is painful, treatment is paused and restarted at a 20% lower dose.
Maintenance and Tapering
- Once maximum response is reached (usually after 20–30 sessions), we move to maintenance by gradually reducing frequency (from 3 times a week to twice, then once a week) before stopping, to prolong remission.
