Patch test, 48 hours
Past use is not protection.
Because sensitisation develops in people who have had the treatment for years without trouble.
Clients reasonably assume that having had lash or brow tint before means they are safe. Sensitisation does not work that way: a reaction can appear after years of uneventful treatments, and reactions to these products can be severe enough to need hospital treatment. The 48-hour test exists because of real cases.
It is also the request salons most often cave on, because the client is in the chair, the appointment is booked and refusing is awkward. Holding the line costs appointments and occasionally annoys people, and it is the clearest signal of whether a salon is run for the client or for the till.
Nail damage follows a similar pattern of misplaced blame. Gel itself is not the problem; peeling or filing it off removes layers of nail plate, and the thin, bendy nails that result get attributed to the product. Soaking off properly takes twenty minutes nobody sees and is the whole difference.
Past use is not protection.
Peeling is what damages nails.
Acne and eczema go to a GP.
A free consultation and patch test first, then the treatment.