ALA-PDT is capable of clinically improving acne. An alternative mode of action for ALA-PDT other than direct damage to sebaceous glands or photodynamic killing of P. acnes is suggested from the results of this study.

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Hypercornification is an early feature of acne and precedes inflammation. It is associated with ductal hyperproliferation and there are many controlling factors such as androgens, retinoids and cytokines. Cycling of normal follicles and of comedones may explain the natural resolution of comedones and, in the longer term, resolution of the disease itself. There is a need to tailor treatment according to comedonal type. Suboptimal therapy can often result from inappropriate assessments of comedones, especially microcomedones, missed comedones, sandpaper comedones, submarine comedones and macrocomedones. Macrocomedones can produce devastating acne flares, particularly if patients are inappropriately prescribed oral isotretinoin. Gentle cautery under topical local anaesthesia is a useful therapy in the treatment of such lesions. The newer retinoids and new formulations of all-trans-retinoic acid show a better benefit/risk ratio. Evidence-based studies are required to allow adequate comparisons.

The success reported for the treatment of superficial skin carcinomas by photodynamic therapy with topical application of the photosensitizer precursor 5-aminolevulinic acid has therapeutic implications for the treatment of other skin disorders. This paper describes the accumulation of the photosensitizing agent protoporphyrin IX in areas of plaque psoriasis by monitoring of the fluorescence emission induced by low-intensity laser excitation at 488 nm. We present results from 15 patients with a total of 42 plaques and show that the characteristic fluorescence emission of protoporphyrin IX increases in intensity within the 6-h period following application of 5-ami-nolevulinic acid, suggesting that there is a potential for superficial photodynamic therapy. The rate of increase and maximum intensity of fluorescence emission was not directly related to the applied quantity of the precursor. The variability of the fluorescence intensity was as great between plaques at different sites on the same patient as between different patients. Also, the effect of plaque occlusion following application appeared insignificant. Although there was only limited enhancement of emission from areas of skin surrounding the plaque, a significant buildup of sensitizer was detected after several days in some areas of psoriasis that received no application.

We have investigated the clinical response of 22 patients with plaque psoriasis to photodynamic therapy using topical application of 5-aminolaevulinic acid followed by a single exposure to broad-band visible radiation. Light doses in the range 2-16 J/cm2 delivered at dose of 10-40 mW/ cm2 resulted in a variable clinical response. Seven (35%) patients showed clearing of psoriasis at some treated sites. The intensity of protoporphyrin IX fluorescence was recorded before, during and after treatment. Pre-illumination fluorescence intensity varied considerably between sites on the same patient and between patients. Protoporphyrin IX fluorescence recovered and persisted after treatment for up to 14 days and became higher than preillumination levels at 25% of sites. The rate of protoporphyrin IX photo-oxidation during treatment was proportional to both initial fluorescence intensity and incident light dose rate and was almost complete after 16 J/cm2. We have defined the photodynamic dose as the product of time-dependent protoporphyrin IX concentration and light dose and demonstrated that only in those patients who showed clearance of psoriasis was there a relationship between photodynamic dose and clinical response. Discomfort ranged from stinging through to burning, was significant in some patients and tended to be more severe with increasing photodynamic dose but was not predictable. Efficacy may improve by achieving consistent protoporphyrin IX levels or by using multiple treatments.

92 children (45 girls, 47 boys), mean age 9.3 years (3-14.75), were referred to the Contact Dermatitis Investigation Unit, Belvidere Hospital, Glasgow, for patch testing during the period 1979-93 for the investigation of allergic contact dermatitis (ACD). The diagnoses at the time of referral were atopic dermatitis (45), non-atopic with localized dermatitis (26), juvenile plantar dermatosis (15), orofacial granulomatosis (2), vaccination reaction (2) and atypical psoriasis (2). In total, there were 55 positive reactions in 30 children. The commonest allergens were metals (18), fragrances (11) and rubber compounds (6). The patient groups with the highest yield of positive patch tests were those patients with atopic dermatitis who had a good history of a precipitating contact factor (4/5), and non-atopic patients with dermatitis of hand and/or feet (7/14). Our findings suggest that allergic contact dermatitis is more common in children than generally appreciated and that patch testing is a practicable and clinically worthwhile procedure in children.

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