Scalp involvement in patients referred for patch testing: Retrospective cross-sectional analysis of North American Contact Dermatitis Group data, 1996 to 2016

BACKGROUND

Scalp conditions are often multifactorial.

OBJECTIVE

To characterize patients with scalp involvement and patch-testing outcomes.

METHODS

Retrospective cross-sectional analysis of North American Contact Dermatitis Group data (1996-2016). Study groups included patients with scalp involvement (≤3 anatomic sites coded) with or without additional sites.

RESULTS

A total of 4.8% of patients (2331/48,753) had scalp identified as 1 of up to 3 affected anatomic sites. Approximately one-third of "scalp-only" individuals had a specific primary diagnosis of allergic contact dermatitis (38.6%), followed by seborrheic dermatitis (17.2%) and irritant contact dermatitis (9.3%). When adjacent anatomic sites were affected, allergic contact dermatitis was more frequently identified as the primary diagnosis (>50%). The top 5 currently clinically relevant allergens in scalp-only patients were p-phenylenediamine, fragrance mix I, nickel sulfate, balsam of Peru, and cinnamic aldehyde. Methylisothiazolinone sensitivity was notable when adjacent anatomic sites were involved. The top 3 specifically identified sources for scalp-only allergens were hair dyes, shampoo/conditioners, and consumer items (eg, hair appliances, glasses).

LIMITATIONS

Tertiary referral population.

CONCLUSION

Isolated scalp involvement was less likely to be associated with allergic contact dermatitis than when adjacent anatomic sites were involved. Overlap with multiple diagnoses was frequent, including seborrheic dermatitis, irritant dermatitis, other dermatoses, or all 3. p-Phenylenediamine was the most common allergen.

Epidemiology of nickel sensitivity: Retrospective cross-sectional analysis of North American Contact Dermatitis Group data 1994-2014

BACKGROUND

Nickel is a common allergen.

OBJECTIVE

To examine the epidemiology of nickel sensitivity in North America.

METHODS

Retrospective, cross-sectional analysis of 44,097 patients patch tested by the North American Contact Dermatitis Group from 1994 to 2014. Nickel sensitivity was defined as a positive patch test for nickel. We evaluated the frequency of nickel sensitivity and patient demographics. For each positive reaction to nickel, we tabulated clinical relevance, occupational relatedness, and exposure sources.

RESULTS

The average frequency of nickel sensitivity was 17.5% (1994-2014). Nickel sensitivity significantly increased over time (from 14.3% in 1994-1996 to 20.1% in 2013-2014 [P < .0001]). Nickel-sensitive patients were significantly more likely to be female, young, nonwhite, and atopic (have eczema and asthma) and/or have dermatitis affecting the face, scalp, ears, neck, arm, or trunk (P values ≤ .0474). Overall, 55.5% of reactions were currently clinically relevant; this percentage significantly increased over time (from 44.1% in 1994-1996 to 51.6% in 2013-2014 [P < .0001]). The rate of occupational relatedness was 3.7% overall, with a significant decrease over time (from 7.9% in 1994-1996 to 1.9% in 2013-2014 [P < .0001]). Jewelry was the most common source of nickel contact.

LIMITATIONS

Tertiary referral population.

CONCLUSIONS

Nickel allergy is of substantial public health importance in North America. The frequency of nickel sensitivity in patients referred for patch testing has significantly increased over a 20-year period.