Add one new active without wrecking your week

A two-week plan to introduce a single serum or acid — so you know what caused a reaction.

2-week planEvening introductions18+

Under 18: stick to first routine; do not run this plan with acids/retinoids without clinician input.

Updated 2026-04-12

If you change three products in one week, you will not know what stung. Introduce one leave-on active at a time.

At a glance

Time: 2-week plan · Best time: evening · Age: 18+ · Basics stay fixed.

Steps

Hold a stable week: same cleanser, moisturiser, SPF.
Patch-test the new active (48 hours).
Use it 1–2 nights in week one only — no other new actives.
If calm, you may increase frequency in week two per label.
Only after two calm weeks consider a second new product.

Side effects

Expected: mild adjustment dryness with some actives.
Stop that product: persistent burn, rash, swelling.

Watch

This is general cosmetic education, not a medical diagnosis or prescription. Persistent rash, swelling, or eye involvement needs a qualified clinician.

Sources

Contact dermatitis education — one change at a time principleIsolating exposures helps identify irritants

General education only — not a substitute for personal medical advice.