PI-WIKI-IMM-28 · Immunology · reviewed 2026-10-28
Immunology, Contact Dermatitis and Patch Testing
Critical numbers
Nickel allergy prevalence (adults)10-17%; 15-25% of women (ear piercing is #1 risk factor)
Cobalt/nickel co-sensitisation25-50% of nickel-allergic individuals
Titanium allergy prevalence<1%, true titanium allergy extremely rare
PPD sensitisation from black hennaA single black henna tattoo can cause lifelong PPD allergy
Type IV sensitisation phase10-14 days on first exposure (asymptomatic)
Type IV reaction latency (re-exposure)24-72 hours
Patch test reading schedule48h (removal), 72-96h (delayed), 7 days (metals)
EU nickel release limit0.2 μg/cm²/week for pierced posts; 0.5 for other skin contact (tested to EN 1811) [9]
316L steel nickel content10-14%, "surgical steel" is not nickel-free
Palladium/nickel cross-reactivity30-40% of nickel-allergic patients
TRUE Test panel size35 allergens + negative control (North American TRUE Test)
Red pigments in reacting tattoosPigment Red 22 and Pigment Red 170 often found; ink patch tests usually negative
Do not
- Assuming all metal reactions are nickel allergy
- Treating ACD with topical antibiotics
- Replacing jewellery with "hypoallergenic" or "surgical steel" without…
- Dismissing delayed tattoo reactions as "normal healing"
- Ignoring PPD sensitisation risk from black henna
- Confusing titanium allergy with mechanical irritation
Applicable standards
- EU / UK — REACH Annex XVII Entry 27 (the former Nickel Directive)
- United States — No federal nickel restriction
- ASEAN / AP — No unified ASEAN nickel restriction; individual member states may reference EU…