The best time of year to start a retinoid (and when to never do it)

The skincare internet treats retinoid timing as personal preference. “Start whenever you’re ready” is the standard line. That’s wrong. There’s a real seasonal calculus to when retinoids tolerate well, when they don’t, and when starting one means you’ll abandon the routine three weeks in because your skin is fighting two things at once: the retinoid adjustment and the environmental insult of peak summer or peak winter.

The sweet spot for most US climates is the second half of September through early November. UV is dropping but still meaningful (which keeps SPF compliance honest), humidity is mid-range, and you have a long runway of stable conditions to climb the dose ladder before either summer sun or winter dryness becomes the bigger variable than the retinoid itself.

Why summer is the wrong season to start

Two reasons. First, retinoids increase photosensitivity in the first six to twelve weeks of use. UV exposure during this period is more likely to cause irritation, post-inflammatory pigmentation, and accelerated barrier disruption. The data on photosensitivity in long-term retinoid users is reassuring; the data on the first three months is not. Starting in June means weeks one through twelve happen in July, August, and September, which is the highest UV window for almost all US zip codes.

Second, summer is the season people are most likely to be inconsistent with SPF. Travel, beaches, sweat, reapplication challenges. The combination of new retinoid use and inconsistent SPF is the recipe for the worst possible first impression. People conclude retinoid “doesn’t work for them” because they tried it in July and ended up with a pigmented patch on their cheekbone.

Why mid-winter is also wrong

Different problem. Indoor heating drops humidity to 15% to 30% in most US homes between December and February. Retinoids cause transepidermal water loss during the adjustment period. Starting a retinoid in January means stacking the retinoid drying effect on top of an already-compromised winter barrier. The visible result is flaking, tight skin, redness, and a much higher chance of abandoning the protocol in week three.

If you live in a cold dry climate (Denver, Minneapolis, Boston, Chicago), this is more important. Coastal climates with mild humid winters (Seattle, San Francisco, Portland) can tolerate January starts better.

The actual start windows by US region

Northeast (Boston, NYC, Philadelphia, DC). Mid-September to late October. Skip January to early March. Skip June to mid-August.

Southeast (Atlanta, Charleston, Raleigh, Nashville). Late September to mid-November. Skip mid-May to mid-September because the UV exposure stays high. Winter is usable.

Midwest (Chicago, Minneapolis, Detroit, St. Louis). Mid-September to mid-October, narrow window. Skip January to February because of very low indoor humidity. Skip June to August.

Mountain West (Denver, Salt Lake City, Albuquerque). Late September to early November, but the high-altitude UV stays meaningful longer, so be aggressive on SPF. Skip December to February (dry winters).

Pacific Northwest (Seattle, Portland). Late September to early December, then March through May. The mild humid winters here are actually fine for retinoid starts.

California coastal (LA, San Francisco, San Diego). October through April. The mild climate widens the start window considerably. Skip May to September because UV is consistent.

Southwest (Phoenix, Las Vegas). November through February only. The combination of intense UV and dry climate makes this the hardest US region to start a retinoid.

The contrarian H2: spring is the worst time to start, not the best

Conventional skincare advice often recommends spring as the retinoid start because “the days are getting longer and SPF habits are easier to remember.” That’s the wrong frame. Starting in March or April means weeks five through twelve happen in May, June, and July, which is when UV index climbs from moderate to extreme in most regions. Your skin is mid-adjustment, peak sensitive, and the environmental load is rising on you. That’s the opposite of the fall pattern, where you start with rising sensitivity and a falling environmental load.

Spring sounds intuitive. The data and the climatology say fall is the answer.

When to wait a full six months

If you’ve had a recent procedure (chemical peel, laser, microneedling) in the last eight weeks, wait. The compounded barrier disruption isn’t worth it.

If you’ve had active acne treatment with isotretinoin (Accutane) in the past six months, wait. Your skin is already in a long recovery from systemic retinoid exposure.

If you’re pregnant or breastfeeding, wait until after. Most topical retinoids are contraindicated, and the ones with weaker contraindications are still standardly avoided.

If your barrier is currently disrupted (eczema flare, perioral dermatitis, sunburn), wait until baseline is restored. Two to four weeks of just gentle cleanser and moisturizer, then assess.

If you’ve moved to a new climate in the past month, wait six to eight weeks for your skin to adjust to the new humidity and UV pattern. Then layer the retinoid.

The real numbers: what trials show about photosensitivity windows

A 2017 review in JAMA Dermatology on topical retinoid photosensitivity concluded that the first eight to twelve weeks of use show measurably increased minimum erythemal dose (MED) reduction, meaning skin burns faster, and that this normalizes after the adjustment period. Studies on tretinoin specifically show MED reduction of 10% to 20% in the first month, returning toward baseline by week sixteen. The implication is that the first three months are the high-risk window, and aligning that window with seasonally lower UV is rational.

A 2014 paper in the Journal of the American Academy of Dermatology on adherence patterns in topical acne treatment noted that seasonal weather was a statistically significant predictor of discontinuation, with summer and deep winter starts showing higher early-dropout rates than fall and spring starts. The patterns held across regions.

What to do if you’ve already started in the wrong season

If you started in summer: pause the retinoid until late September. Spend the summer building barrier strength with niacinamide and ceramides. Restart fresh in the fall.

If you started in deep winter: don’t pause if you’ve made it past week six, you’re through the worst of the adjustment. But run a humidifier, use a richer moisturizer, and consider buffering the retinoid (apply moisturizer first, wait fifteen minutes, then apply retinoid over) for the rest of the winter.

If you started in the right window and your skin is going great: keep going. The seasonal advantage compounds over time.

FAQ

Q: Can I start a retinoid in tropical climates? A: Year-round UV makes the timing question different. The answer is usually “during the rainy season” if there is one, or “whenever you can commit to indoor-leaning weeks for the first month.” Hawaii and Miami are harder to time than Denver.

Q: Does this advice apply to prescription tretinoin too? A: Yes, more so. Tretinoin’s photosensitivity window is longer and more pronounced than over-the-counter retinol. The seasonal timing matters more, not less.

Q: What if I want to start now and it’s the wrong season? A: Use an encapsulated very-low-strength retinol (0.1% to 0.2%) twice a week and treat it as a holding pattern until the right window. Don’t start the main protocol out of season.

Q: Are bakuchiol or retinal exceptions? A: Bakuchiol has much less photosensitivity data and likely a smaller seasonal effect. Retinal (retinaldehyde) behaves similarly to retinol and the same timing applies.

Q: How strict should I be about this? A: Strict for very fair skin (Fitzpatrick I-II) and skin with a history of melasma or post-inflammatory pigmentation. Less strict for darker skin types where photosensitivity reactions present differently. Always strict on the SPF, regardless of when you start.

For related reading, see our first retinol night walkthrough, the retinol tag, and our winter skincare archive.

Sources

Mukherjee S et al. Retinoids in the treatment of skin aging. Clinical Interventions in Aging, 2006 (PubMed). Kong R et al. A comparative study of the effects of retinol and retinoic acid on human skin. Journal of Cosmetic Dermatology, 2016 (PubMed). AAD.org/” rel=”noopener” target=”_blank”>American Academy of Dermatology. Retinoid or retinol? AAD Public Education, 2023.