How long is a patch test valid?

The short version most columns use

For lash adhesive, a very common starting point is a test at least 24 hours before the first full set, valid for about six months, and a new test if the adhesive changes or they have been away longer than that window. For tint, some houses want 48 hours. For PMU pigment, 48 hours and six months is a frequent default. None of those sentences is a law. They are the numbers a lot of UK policies and training manuals repeat.

Hair colour is a different vocabulary and a different article: hairdressers say allergy alert test or skin test, not patch test, and the usual lead is 48 hours.

This is a working explanation for people who do the job, not legal, insurance or medical advice. Read your own policy, your local authority, and the current wording from the bodies named. Glow records what you set. It does not decide the rule and it does not claim a salon is compliant.

Why 'how long' is the wrong first question

The first question is 'valid for what?'. A test that passed in January on adhesive A does not speak to adhesive B in July. A test done behind the ear for a tint does not automatically cover a new lash glue. A client who had a reaction in another salon and did not tell you has a history your six-month sticker cannot see.

Validity is a policy you choose so that, later, you can show: this client, this product family, this date, this result, this signature. If you cannot show those five, the number of months on a Facebook post will not help.

What insurers and trade bodies tend to talk about

Beauty insurers in the UK typically treat a missing or out-of-date test as a reason to refuse a reaction claim, not as a paperwork slap on the wrist. The exact hours and months sit in the schedule you signed. Some want 24 hours, some 48. Some want six months, some 12, some 'every time the product changes'. Read the schedule. If you cannot find the paragraph, email them and keep the reply.

Training bodies and membership organisations (NHBF among them) talk about record-keeping as part of running the salon: who, when, what, outcome. They do not all publish one shared table of hours. That is why two techs in the same town can both be 'doing it properly' with different numbers — they are following different policies.

Product houses (adhesive, tint, pigment) often print a recommended test method on the IFU. If you ignore the IFU and something happens, you are arguing with both the insurer and the manufacturer. Keep the IFU with the batch.

Lead time versus expiry

Lead time is how long before the treatment the test must have been done — 24 or 48 hours is typical — so a delayed reaction has a chance to show. Expiry is how long after a pass you will still honour it. Mixing those two up is how people book a 'test' at 9am and a full set at 10am and call it done.

A same-day test is a different decision. Some insurers forbid it. Some allow it with a signed waiver that is worth less than people think when a claim arrives. If you offer same-day, that is your policy, written down, not a vibe.

What to record so the window means something

Date and time of the test. Product name and batch. Where it was applied. Result (pass, fail, they did not come back). Signature. Which treatment it unlocks. When it expires. If they failed, what you did next.

A photo of a red patch on a phone is not a record unless it is attached to that client and that date. A tick on a paper card with no batch is a record of a tick.

Glow's default for lashes is 24 hours' lead and six months' validity, and the public page will not let them book the treatment if that has lapsed. You can change both numbers. Glow for lash techs is the product page. Pricing is £19 a month.

When to retest even if the window is still open

New adhesive, new tint brand, new pigment line. A gap in visits longer than your policy. Pregnancy, medication changes, or a skin condition they mention at the desk — those are clinical judgements, not software settings. A reaction last time, even a mild one. A client who had black henna since you last saw them.

If you are unsure, do not invent a rule on the doorstep. Sit them for a test and move the treatment. The hour you lose is cheaper than the file you cannot produce.

A worked example so the numbers are not abstract

Monday: new client books a classic full set for Saturday. The page also books a Tuesday patch test because you set 24 hours' lead. Tuesday: they sit, you apply the adhesive you actually use, you write the batch, they leave. Wednesday you mark a pass. Saturday they sit for the set. The test is three days old. The window has years left. Fine.

Six months and a week later they book a fill. If your expiry is six months, the page treats them as untested. They are annoyed. You are not arguing from a caption. They book a new test. If they had come at five months and 28 days, the fill goes through. That is all an expiry is: a date you chose, applied evenly, instead of a vibe at the door.

If on the Saturday you had opened a new adhesive, a careful column would have retested or at least written that the lot changed. Software cannot smell a new bottle. You still have to say so.

What Glow will and will not do

Glow will store the test on the client, expire it when you said it should expire, and refuse the online booking when it has lapsed. It will sit the batch next to the visit. It will not phone your insurer. It will not tell you that six months is 'the legal period'. There is no single legal period for a lash patch test in the UK.

If you want the longer version of a missing file, read what happens if a client reacts and you have no test on record.