PUVA-induced diminution of contact allergic and irritant skin reactions

Abstract

Summary A pilot study on the efficiency of treatment with 8‐methoxypsoralen and longwave ultraviolet light (PUVA) on three patients with allergic contact dermatitis to nickel sulphate, potassium dichromate and to thiuram mix has been performed. Both the contact allergic reactions and the irritative skin reactions induced by dimethyl sulfoxide (DMSO) and tetrahydrofurfuryl nicotinate (Trafuril) were evaluated before and after PUVA. The total UV‐A doses were respectively 69–45 and 76J/cm2. These doses induced complete clearance of the eczematous lesions in two cases; the third case showed considerable improvement. In contrast to the pronounced skin reactions seen prior to PUVA, the allergic and irritative reactions evaluated after PUVA were decreased or negative.

How does PUVA inhibit delayed cutaneous hypersensitivity?

“…An inhibitory effect on expression was also shown by our previous experiment (Moss et al1 981) in which patients sensitized before PUVA and challenged during PUVA were less reactive than untreated patients. Similarly, Thorvaldsen & Volden (1980) showed that expression of established contact hypersensitivity to common allergens such as nickel is reduced by PUVA, and Morison et al (1981) found reduced expression of contact sensitivity to DNCB in PUVA-treated guinea-pigs. However, in none of these experiments was a local mechanism distinguished from a systemic effect of PUVA.…”

“…This might be immunological (mediated by either T lymphocytes or Langerhans cells) or simply an effect of PUVA on the mediators of inflammation in the skin. Thorvaldsen & Volden (1980) found that PUVA reduced the irritant response to thurfyl nicotinate and dimethyl sulphoxide, but this possibility needs further study.…”

European Society of Contact Dermatitis guideline for diagnostic patch testing – recommendations on best practice

“…Exposure to UVB may reduce the risk of sensitization and temporarily diminish the ability to elicit allergic reactions in sensitized individuals. Although this seems not to be the case for UVA (110,111), psoralen combined with UVA has been reported to cause a reduction in patch test reactions (112). UV irradiation results in a reduction in epidermal Langerhans cell numbers (113).…”

Effects of PUVA on delayed hypersensitivity in the guinea-pig

“…This effect is temporary and can only be demonstrated in the treated area of the skin. PUVA therapy of patients with allergic contact dermatitis improves the dermatitis, and patch tests demonstrate a diminution of the allergic reaction after therapy (Thorvaldsen & Volden, 1980). In psoriasis patients receiving PUVA therapy, there was found either abnormally low or undetectable delayed hypersensitivity reaction in the skin, as judged by the DNCB test (Strauss et al, 1980).…”