Support

How does the app work out how long my session should be?

Three things: the UV index where you are, your skin type, and which of the twelve sessions you are on.

Underneath all three sits one measurement: the minimal erythemal dose, or MED — the amount of ultraviolet that would just barely turn your skin pink. It depends on skin type, and it is a physical quantity rather than a rule of thumb. Every session in the programme is defined as a fraction of your MED: 20% on the first session, rising in eight steps to 64% on the last. Even the final session of the programme stays a third below the point where skin reddens.

Minutes are then arithmetic. Dose is strength multiplied by time, and a UV index of 1 means 25 milliwatts per square metre, so the app divides the session's dose by how strong the sun is where you are standing. That is why the same session runs about twice as long at UV 3 as at UV 6 and about half as long at UV 11 — and why two people on session three with different skin types are given different numbers of minutes for exactly the same risk.

When the sky is patchy the app deliberately plans for the worst case. Broken cloud is the dangerous condition — the forecast UV reads low, but the moment the cloud moves you get almost the full clear-sky dose — so at around 50% cloud the app plans as though the sun were fully out. This only ever shortens a session.

There is no separate safety ceiling on top of this, because there is nothing left to cap: the dose is the limit, and the minutes are simply whatever delivers it. When the sun is weak a session can run long — at most about an hour, and only on the last session with the darkest skin type — and the app warns you before you start rather than quietly cutting it short. A shortened session that still counted as completed would move you up the programme on a dose you never actually received.

Why did my session get shorter while it was running?

Because the sun got stronger than the forecast said. Every three minutes the timer checks the live UV index, and if it has risen above what the session was planned for, the remaining time is cut so the total dose stays the same. Clouds passing the other way do not extend your session — if they did, the sun coming back would overshoot.

Why does the app say there is no point tanning right now?

Below UV 3 there is essentially no tanning response, and after sunset there is none at all. Rather than offer you a very long session that achieves nothing, the app tells you to wait. This is also why it will not treat UV 0 as an invitation to sunbathe all evening.

How do I choose my skin type?

Pick by how your skin behaves after a first strong day in the sun, not by how tanned you are now. If you are between two, choose the lighter one — the app will then be more cautious.

You can change it later in Settings → Skin Type. The range runs from the first session to the twelfth at a reference UV index of 6; stronger sun shrinks those minutes proportionally, weaker sun stretches them. Different types get different minutes for the same session because they are taking the same share of a different threshold.

How long is each session?

The table shows the sun-exposed time for every session at the reference UV index of 6, before the live sun adjusts it. Stronger sun shortens these minutes in proportion and weaker sun stretches them; the shade rest at the end is fixed and never changes.

Sun time is split across four positions: front and back take 30–35% each, and each side 15–20%. A full session is the sun time plus the shade rest — from about 7 minutes on session one for very fair skin to about 48 minutes on session twelve for the darkest type.

Why is there a pause between sessions, and why is it a different length each time?

Because sunburn is not visible immediately. Erythema takes 12 to 24 hours to show, so going out again too soon means adding a dose to damage you cannot see yet.

The pause is proportional to the dose you just took, then stretched if your skin reacted. A short early session does not need the same recovery as a long one:

My skin went pink, or red. What happens?

• Fine — you move on to the next session.
• Pink — the programme does not advance. The same session repeats, because your skin has just told you that dose was already at its limit. The rest period is extended by half.
• Red — the programme steps back two levels, so your next attempt is a smaller dose than the one that did the damage, and the rest period is doubled. Stay out of the sun until you have fully healed.

Answering honestly is the whole point: the reaction is the only feedback the app gets about your actual skin, as opposed to the statistical skin type you selected.

What is a MED?

The minimal erythemal dose is the smallest amount of ultraviolet that produces a just-perceptible reddening of the skin. It is measured in joules per square metre and depends on skin type: the fairer the skin, the less it takes. Because the app works in MED, a session can be expressed as a fraction of your own threshold instead of a fixed number of minutes.

The values used are the medians of a study that measured MED in the full solar spectrum (UVA + UVB) alongside a Fitzpatrick assessment: 22 mJ/cm² for types I–II, 33 for type III and 43 for type IV. The app separates types I and II inside that range — otherwise it would ask you a question and then behave identically whichever you answered — and places type I lower still, because professional salons decline that type outright while the app accepts it. The darkest setting is labelled V–VI but carries the study's type IV median: types V–VI were not measured separately, and their real MED is higher, so the app under-doses the most resistant skin rather than inventing a number for it.

The same study makes a point worth repeating: the spread of MED within one skin type is wider than the difference between types. Skin type is a good starting point, not a guarantee. That is why the app asks how your skin actually reacted after every session, and why that answer overrules the table.

On 13 September 2026 these values were checked again against independent measurements, and they hold. A Spanish multicentre study of 232 volunteers found mean MEDs of 23, 28, 35 and 51 mJ/cm² for types I to IV — the app sits below every one of them. Fitzpatrick's original 1988 ranges contain the app's figures for types I, III and IV, and the Fair type sits just under its range, on the cautious side. The European Commission's scientific committee on sunbeds uses 200 J/m² as the MED of sun-sensitive skin — the app's Very Fair value. No session in the programme reaches the threshold of any of these sources.

Why are the first sessions so short?

The first session delivers about 20% of your MED, which is close to what a professional tanning salon gives a first-time visitor: one to two minutes for fair skin and four to six for dark, at the 0.3 W/m² irradiance limit that applies in Europe.

Medical phototherapy starts far higher, at 50–70% of MED, but that is treatment under supervision, where a quick result is wanted and a reaction can be managed. In a study of 352 patients on that schedule — starting at 70% and increasing 20% per session — about 60% had reddened by the twentieth session. That pace is not appropriate for tanning without supervision, which is why the app does not borrow it.

Why does the programme stop at session twelve?

Sessions one to eight build up, and the eighth delivers about 64% of MED. Sessions nine to twelve consolidate: each adds only 4% of MED, and the twelfth delivers 80% — deliberately a fifth below the reddening threshold, and deliberately below the industry maximum. The "maximum times" printed on commercial sunbed charts work out at roughly 100% of MED, which is to say exactly at the threshold, and a sunbed's own 30-minute cut-off comes to about 126% for dark skin.

Only skin that has finished session eight without reddening gets that far: a session that turns your skin pink is repeated, and a burn moves you back two. The margin is counted against skin that has not adapted at all; after eight sessions yours usually has, so the real margin is larger. After session twelve the app keeps you at that level rather than inventing higher ones. A tan is maintained at that dose; it is not improved by pushing past it.

What the app deliberately does not do

• It does not model adaptation. Skin builds its own protection over a course of sun exposure and its real MED rises; the app keeps treating your MED as fixed, so its error is always on the cautious side. In the study cited below, that adaptation did not depend on skin type.
• It does not replace sunscreen and it does not remove risk. Any ultraviolet exposure raises the risk of skin cancer and photoageing. The app lowers the chance of a burn; it does not make sun exposure safe.
• It is not for everyone. If you have a photodermatosis, take photosensitising medication, have a history of skin cancer or a large number of moles, talk to a doctor before using it at all.

Do I have to allow location access?

No, but it makes the app considerably more useful. Location is what lets it fetch the real UV index where you are standing. Your coordinates go to the weather service and nowhere else, and are never stored — see the Privacy Policy.

If you refuse, the app still works. It falls back to an estimate based on your latitude and deliberately errs short, so your sessions will be more conservative than they need to be.

Why does the app ask to send notifications?

For two things: telling you to change position during a session, and telling you when your rest period is over. A "turn onto your back" prompt that arrives late is a burn, which is why the timer needs to reach you even when your screen is off.

These are scheduled on your own phone. Nothing is pushed from a server, and the app holds no notification token.

I changed phone. How do I get my purchase back?

Open the payment screen and tap "Restore Purchases", signed in to the same App Store or Google Play account you originally bought with. The purchase is tied to that store account, not to your Suntan Workout login.

How do I cancel my subscription?

Subscriptions are held by the store, so they are cancelled there — not in the app, and not by deleting your account.

• iPhone or iPad: Settings → your name → Subscriptions → Suntan Workout → Cancel Subscription.
• Android: Google Play → your profile picture → Payments and subscriptions → Subscriptions → Suntan Workout → Cancel.

Cancel at least 24 hours before the period ends, otherwise it renews once more. You keep access until the end of the period you have paid for.

Can I get a refund?

Refunds are handled by Apple and Google, since they took the payment. Use reportaproblem.apple.com, or the order history in the Play Store. We cannot issue a refund ourselves, though we are happy to help you make the case.

Do I need an account?

No. Without one the app works fully, and your progress stays on the device — nothing is uploaded. An account exists so your history survives a lost phone and follows you to a new one.

How do I delete my account and everything in it?

Profile → Delete Account. That removes your login and every session recorded against it, permanently and immediately.

If you have already uninstalled the app, write to info@emaho.dev from the address on the account and we will do it for you. Remember that deleting the account does not cancel a subscription — that has to be done in the store.