Scanning one product tells you what's in that bottle. It doesn't tell you what happens when you use it alongside the other six things on your shelf. Yarai checks every product in your routine against every other product, and grades what it finds.
Most ingredient apps analyze one product at a time. That model can't see the problem most people actually have, because the problem isn't in any single bottle. Two products can each be well formulated and still be a bad combination: one may degrade the other on contact, or their irritation may simply stack past what your skin tolerates.
Routines also grow by accident. You add a product for one concern, another for a second, and end up with three sources of exfoliation you never chose as a set. Nothing on any individual label warns you about that. Only something looking across the whole routine can.
Yarai builds your AM and PM routine, then evaluates every pair of products in it, not just the one you scanned most recently. Add a seventh product and it is checked against the six already there. Reorder your evening steps and the analysis updates.
Each conflict comes with four things: the severity, the mechanism, the evidence behind it, and the condition under which it actually applies. That last one matters most, because most conflicts have a scheduling fix rather than a "throw the product away" fix.
| Combination | Severity | What Yarai tells you |
|---|---|---|
| Retinoid + benzoyl peroxide | Medium | Benzoyl peroxide can oxidize many retinoids and weaken them. Separate by time of day or alternate days. Adapalene is stable with benzoyl peroxide, so combination products built around it are exempt rather than flagged. |
| Retinoid + glycolic acid | Medium | Both raise cell turnover, so irritation stacks. Tolerance-dependent, not a hard incompatibility. Alternating nights is the usual path while skin acclimates. |
| Retinoid + salicylic acid | Medium | Same additive irritation. Acid in the morning and retinoid at night resolves it for most people, or alternate days. |
| Retinoid + mandelic acid | Low | Mandelic is one of the gentler exfoliants, so this is graded lower than the glycolic pairing, but it can still add up on sensitive skin. |
| Benzoyl peroxide + salicylic acid | Medium | Both dry and irritate. Dermatology guidance treats them as legitimate combination therapy for acne, so the flag is about introducing them gradually, not avoiding the pair. |
| Hydroquinone + benzoyl peroxide | Low | Benzoyl peroxide can oxidize hydroquinone on skin and cause temporary brown staining. Different times of day, with washing in between, avoids it. |
| Niacinamide + vitamin C | Not flagged | Deliberately not treated as a conflict. See below. |
The niacinamide and vitamin C myth: plenty of apps and articles still tell you to separate these. The claim traces to a 1960s study using pure unstabilized ascorbic acid under conditions nothing like a modern formulation. Yarai had that rule and removed it. A conflict checker is only worth trusting if it deletes rules that turn out to be wrong, not just accumulates new ones.
A checker that only says "warning" leaves you with nothing to do. Yarai grades conflicts from minor (space these apart) to significant (don't combine), and shows the mechanism behind each one: oxidative degradation, additive irritant load, oxidative staining. Every rule carries an evidence tier, from mechanistic reasoning through dermatology consensus to randomized controlled trial, and cites its source.
The practical difference: instead of being told a product is a problem, you're told whether to reorder your steps, separate them by hours, or move one to alternate nights.
Retinoid rules apply to the whole retinoid class rather than a hardcoded list of product names. Retinol, retinaldehyde, tretinoin, adapalene, and retinyl esters all inherit the rule, which means an unusual or newly launched retinoid is covered the day you scan it.
Conflict severity is read alongside dosage-aware scoring: Yarai estimates roughly how much of each ingredient is present from its INCI list position and judges it in context. An active at a trace level and the same active at a full dose do not carry the same weight. That's the same concentration-based analysis used for single-product scores.
The routine builder is where conflicts get resolved. Order products into a morning and an evening routine, or run a skin cycling schedule where actives rotate across nights. Because most flagged pairs are timing problems rather than product problems, the fix is usually a change to the schedule rather than a purchase.
Conflict checking only helps if every product in your routine can actually be read. Yarai scans the front label directly with your camera, with no barcode and no database lookup, so imported products, indie brands, decanted bottles, and anything without packaging still enter the routine and get checked. Barcode-dependent scanners drop these products with a "not found," and a routine analysis with holes in it isn't a routine analysis.
A routine conflict checker looks at all the products you use together rather than one product in isolation, and flags pairs that interact badly. Two products can each be well formulated and still be a poor combination, either because one degrades the other or because their irritation stacks. Yarai checks every pair of products in your AM and PM routine and grades each conflict by severity.
Both increase cell turnover, so combining them can stack irritation, redness, and peeling. This is tolerance-dependent rather than a hard incompatibility: supervised combined use is common, and alternating nights is the usual approach while skin acclimates. Yarai grades this as a medium-severity conflict and suggests the scheduling fix rather than telling you to drop a product.
Benzoyl peroxide can oxidize many retinoids and reduce how well they work when applied at the same time, which is why Yarai flags the pair and suggests separating them by time of day or alternating days. Adapalene is stable with benzoyl peroxide, so combination products built around it are exempt from the rule rather than flagged.
No. This is a persistent myth traced to a 1960s study using pure unstabilized ascorbic acid under extreme conditions that do not resemble modern formulations. Yarai deliberately does not flag this pair.
Each rule carries a severity level, a mechanism, an evidence tier, and a dose condition describing when the conflict actually applies. Minor conflicts mean space these apart; significant conflicts mean don't combine. The reasoning and the source are shown with the flag.
Every rule above has its own page with the mechanism, evidence tier and source: see the full conflict library. Related: the ingredient analyzer for single-product scanning, and routine creep and the conflicts hiding in your shelf.
Yarai is free to scan and analyze. Premium features (unlimited AI routines, full conflict detection) are available via optional subscription: $2.99/month or $19.99/year, with a 7-day free trial. Yarai does not provide medical advice. Consult a dermatologist for specific skin concerns.