What a reaction looks like
Early: itching, swelling, blistering or a rash at the site within hours to days. Delayed: a lumpy, itchy, sometimes scaly reaction (granulomatous or lichenoid) weeks to years later, classically to certain reds. Because the pigment cannot simply be washed off, delayed reactions can require steroids, laser or excision.
Patch testing
A small amount of the intended pigment is implanted (not just dabbed on) in a discreet spot — behind the ear, inner arm, or hidden lower-lip margin — and reviewed at 24–48 hours and again at 2–4 weeks. It is most worthwhile for clients with multiple allergies, prior pigment/metal reactions, or reactive skin.
Its limits: a delayed allergy can still develop after a clear patch test, and a topical dab test under-predicts an implanted reaction.
Documentation
Record the exact product and batch tested and the outcome. If a client reacts, report it to the pigment manufacturer and your regulator, and give the client the product details to take to a dermatologist.
