Saudade Gonçalo

Hypersensitivity to thimerosal : the sensitizing moiety

There has been increasing interest in characterizing the sensitizing moiety of thimerosal [TIM]. following the finding that patients with photosensitivity to piroxicam arc allergic to the thiosalicylic acid [TIO] moiety of TIM. For this purpose, the authors have conducted 2 studies in TIM‐sensitive patients. In the 1st. of 175 patients tested with TIO and ammoniated mercuric chloride [HGAM|, 45.7% reacted only to TIM, whereas 45. 7%. reacted also to TIO and 17.7%. also to HGAM: 9.1% reacted to both TIO and HGAM. In the 2nd. of 47 patients tested with TIO and ethylmercuric chloride [F.THG], 87.2% reacted to ETHG. 44.7% to TIO and 31.9% reacted to both. None of the patients reacted only to TIM. The authors conclude that thimerosal allergy is due either to the mercuric moiety or to thiosalicylic acid, with no cases of sensitivity only to the whole molecule of TIM. TIM‐sensitive patients are mainly allergic to the mercuric moiety. but among them there are a large number of TIO‐sensitive patients, and these should be advised to avoid piroxicam.

Contact and photocontact sensitivity to sunscreens

Clinical case A 55-year-old man had grown Pleurotus ostreatus for 5 years. He had a previous history of chromate dermatitis from the age of 20 years, with recurrent clinical manifestations that had disappeared 10 years previously, when he left the construction industry because of an accident. From around 6 years, he had had allergic rhinitis, with a total IgE of 361 kUI/L and with prick tests and RASTs highly positive to Parietaria officina/is and negative to other inhalant allergens. For around 3 years, red scaly vesicular lesions had been appearing on the hands, with reported episodes of spread to the upper and lower limbs, face and trunk. Clinical manifestations appeared simultaneously with cycles of harvest of the mushrooms. In particular, episodes of spread were associated with collecting the mushrooms in an advanced stadge of maturation, when the air inside the building was saturated with spores, visible as a dust. Patch tests, with the GIRDCA standard and agriculture series confirmed the already-known positivity to potassium dichromate 0.5% pet., and found a new one to dinocap 1% pet., used by the patient in the past as a pesticide. The lamellae, stem and spores of the mushroom, tested as is, all gave a positive reaction (02 ++I D4+ + .). 30 controls, 10 of them carrying out the same cultivation, were negative. Negative open and prick tests with Pleu,.Jtu;., excluded immediate-type allergy.

Piroxicam‐induced photosensitivity

During the last 3 years, 9 patients with a photosensitive eruption related to piroxicam therapy were seen. In all but one, it occurred within 4 days of first exposure to the drug. 7 patients required systemic corticosteroids, and 2 hospitalization, Clinical, histological and provocation studies were not conclusive in classifying the eruption as photoallergic or phototoxic. Experimental studies including photohaemolysis, Bacillus subtilis culture and nuclear magnetic resonance showed: (i) in irradiatd piroxicam solutions, there was more haemolysis; (ii) in irradiated Petri dishes, piroxicam solutions showed greater inhibition of growth of B. subtilis; (iii) Piroxicams NMR spectrum is not modified after irradiation. The results provide evidence of piroxicam phototoxic potential.

Contact dermatitis to lichens

Contact dermatitis to lichens has been known since 1948, when Tenchio (1948) published cases in woodworkers. They showed positive patch tests to Parmelia caperata, present on the wood where they worked. Le Coulant & Lopes (1956) described a lichen acid with allergic and probably also antibiotic properties. Subsequently several papers were published by Champion (1965), Mitchell (1965), Hjorth et a!. (1976), Thune (1977), Wennersten (1979), Dahlquist & Fregert (1980), all of them confirming the allergenic properties of lichens. Recently new lichen acids have been discovered, characteristic of each species of lichen, which are the etiological agents of contact allergy. Contact dermatitis to lichens is not very frequent. In the last 2 years we have seen eight cases, seven men and one woman, whose ages varied between 29 and 74 years; seven of whom were rural workers and one a forest worker (Table 1). The clinical manifestations were erythema and scaling and sometimes also swelling, vesicles and itching. They were usually localized in light-exposed areas or round the waist, and less frequently were generalized. The lesions appeared between November and March, at the time of the olive crop, or when pruning or cutting olive trees covered with lichens. The lichens contact the skin directly from the tree trunks, or they are reduced to small particles and set free during the mechanical process of beating or cutting the trees; these small particles accumulated on exposed areas or under the clothing, especially around the waist. The eruption recurred in the same circumstances, but with increasing intensity. In the less severe cases they disappeared spontaneously when contact ended. The duration varied from 1 to 8 years. The eight patients were tested with European Standard Test Series (Trolab, Copenhagen), with two species of lichens, Parmelia reticulata and Ramalina lusitana, that grow on olive trees in central Portugal, as well as their alcoholic, ether, ketonic, aqueous and oil ex-

Allergic contact dermatitis from Dittrichia viscosa (L.) Greuter

9 cases of contact sensitivity to Dittrichia viscosa, mainly with an airborne pattern, aree described. All patient reacted to the fresh leaf of die plain and to its ethereal extracts at 1 and 0.5% pet., and some of them also to that at 0.1% pet. Positive reactions to Frullania dilatata, Laurus nobilis, some other members of the Composite, and helenin were observed, suggesting the diagnosis of a sesquiterpene‐lactone‐induced allergic contact dermatitis.