A. Forsyth

Thiomersal allergy and vaccination reactions

Thiomersal is the preservative in all toxoid vaccines routinely administered to children in the UK, but exposure from other sources is uncommon. Delayed hypersensitivity to thiomersal was demonstrated in 1% of individuals attending the Contact Dermatitis Investigation Unit, and 50 of these patients with positive patch tests to thiomersal were studied. Cross‐reaction with other mercurials occurred in 17 of 29 patients tested (59%). 31 of the patients replied to a questionnaire regarding vaccination reactions, and were compared with case‐controls matched for age, sex, and site of dermatitis. 4 patients in each group reported reactions to vaccines which contained thiomersal. Suggesting that thiomersal hypersensitivity wits not associated with an increased risk of vaccination reactions. However, individual cases of severe reactions to thiomersal demonstrate a need for vaccines with an alternative preservative

Contact sensitivity to menthol and peppermint in patients with intra‐oral symptoms

We report 12 cases of contact sensitivity to the flavouring agents menthol and peppermint oil in patients presenting with intra‐oral symptoms in association with burning mouth syndrome, recurrent oral ulceration or a lichenoid reaction. The patients were referred from the Glasgow Dental Hospital over a 4‐year period for assessment of the possible contribution of contact sensitivity to their complaints. 5 patients with burning mouth syndrome demonstrated contact sensitivity to menthol and/or peppermint, with 1 patient sensitive to both agents, 3 positive to menthol only and 1 to peppermint only. 4 cases with recurrent intra‐oral ulceration were sensitive to both menthol and peppermint. 3 patients with an oral lichenoid reaction were positive to menthol on patch testing, with 2 also sensitive to peppermint. 9 of the 12 cases demonstrated additional positive patch test results. After a mean follow‐up of 32.7 months (range 9–48 months), of the 9 patients that could be contacted, 6 patients described clearance or improvement of their symptoms as a consequence of avoidance of menthol/peppermint.

Allergy to non-toxoid constituents of vaccines and implications for patch testing

We report 3 patients with persistent symptoms at vaccination sites. All were allergic to aluminium and one to thiomersal and neomycin too. Aluminium allergy causes false positive patch test reactions and we propose methods of patch testing patients with symptoms at vaccination sites in order to avoid this problem. The practical relevance of allergy to non‐toxoid constituents of vaccines is discussed.

Thermographic assessment of patch‐test responses

Infra‐red thermography was used to quantify, at patch test sites, the allergic responses to experimental preparations of nickel sulphate and primary irritant responses to sodium lauryl sulphate in small groups of volunteers. The technique was also used to assess the patch‐test responses in a much larger group of patients who had undergone routine patch testing for contact allergy with a wide range of test substances and among which there were large numbers of allergic, irritant and equivocal reactions. Thermographically, when compared to the surrounding normal skin surface, the sites of allergic reactions appeared as hot areas, the temperature and area of which were apparently dependent on the severity of the response. For allergic responses, there was a good correlation between the clinical assessment and either of two thermographic parameters, temperature and area of involvement. Compared with an aqueous solution of nickel sulphate, ‘poor’ formulations of the allergen, such as a suspension in soft paraffin base, elicited smaller and cooler reactions. Irritant reaction sites were not ‘hot’ and the temperature at such sites was no different from that of the surrounding normal skin. Infra‐red thermography is a convenient non‐invasive technique which apparently can be used to discriminate between irritant and allergic responses and to quantify the latter type of response.

The genetics of allergic contact hypersensitivity to nickel

We have examined evidence for familial disposition to nickel allergic contact dermatitis (Ni ACD). 258 patients attending for routine patch testing were recruited prospectively. 39 patients were diagnosed with Ni ACD. 31 of 209 1st‐degree relatives (15%) of probands had a history of nickel hypersensitivity. 84 patients with no history of nickel hypersensitivity and negative patch tests to nickel were used as controls. 24 of 458 1st degree relatives of controls (5.2%) had a history of Ni ACD. The risk ratio for 1st degree relatives of a patient with Ni ACD is 2.83 (95% condence intervals are 2.45, 3.27). This is the 1st study to present a statistic to represent risk to relatives of developing ACD. Relatives of patients with Ni ACD have an increased risk of developing the condition, but the genetic basis for this is not yet known. With currently available techniques, this value of relative risk makes a positional cloning approach to gene identication impractical.

Patch testing for nickel allergy The influence of the vehicle on the response rate to topical nickel sulphate

A group of 43 patients with a clinical history of nickel allergy who exhibited an equivocal or no allergic reaction to a patch test al 48 h were further challenged using several different formulations of nickel sulphate. This experimental test battery comprised aqueous, dimethyl sulphoxide (DMSO) and propylene glycol(PG) solutions of nickel sulphate, and nickel sulphate incorporated into cetomacrogol cream and yellow soft paraffin (PMF).

A controlled study of gold contact hypersensitivity

1203 patients attending for routine patch testing at 3 hospitals and 105 volunteers were tested with 0.5% and 0.05% gold sodium thiosulfate (GST). 38 patients (3.2%) and 5 volunteers (4.8%) had positive patch tests to GST. There were no significant differences between volunteers and patients with respect to age, sex, atopy or exposure to gold in dental restorations, jewellery or through occupation. There were no significant differences in prevalence of GST hypersensitivity in the 3 hospitals, or between patients and controls. This is the 1st controlled study of hypersensitivity to GST, and suggests that routine patch testing to gold is of limited clinical benefit.

Patch testing in discoid eczema

We report a retrospective study of patch testing in patients with discoid eczema. 48 patients with persistent or severe discoid eczema were patch tested. The mean age of patients was 45 years and the median duration of symptoms was 6 months. 24 patients (50%) had positive patch tests, and 16 of these (33%) were considered to be clinically relevant. The most common allergens implicated were rubber chemicals, formaldehyde, neomycin, chrome, nickel (5, 2, 2, 2, 2, 2 reactions, respectively). 13 of 16 patients were followed up by telephone in 1996, and 8/13 (61%) slated they had benefited from patch testing. This study suggests allergic contact dermatitis is relatively common in persistent discoid eczema, and allergen avoidance may be of benefit. We recommend patch testing should be considered for all patients with severe or persistent discoid eczema.

Contact sensitivity to cigarettes and matches.

The results of patch testing with a series containing components of cigarettes and matches were reviewed. 2 years were reviewed, 1987 and 1997. 314 patients were patch tested to this series, 203 in 1987 and 111 in 1997. 31 patients had clinically relevant positive reactions to the series, 25 in 1987 and 6 in 1997. 26 patients had relevant positive tests to cigarette components in the series. There were 14 relevant positive reactions to phosphorus sesquisulfide in 1987 and one in 1997. All patients with relevant positive reactions to red match tips also had reactions to phosphorus sesquisulfide. There was a significant association between cigarette and fragrance hypersensitivity. The eczema in 3 of 4 patients who stopped smoking improved. A series containing match heads, smoked cigarette filters and remnants of tobacco from smoked cigarettes may be useful in smokers with eczema of the face, neck or hands.

The trend of allergic contact dermatitis in the elderly population over a 15-year period

Allergic contact dermatitis (ACD) in the elderly (>65 years) is reported to be less common than in the younger adult age group (<65 years) (1, 2). suggesting that elderly patients may not react to allergens so efficiently (3-5). The positive reactions that do occur tend to be many and various ( 6 ) , though reportedly similar to those of the younger age group 17). the most common allergens seeming to be topical medicaments ( 2 , 8, 9). We have compared patch test results in elderly patients of our tertiary referral centre in 2 separate years with an interval of 15 years between them.