Seasonal Glycolic Acid Adjustments: Summer, Winter & Travel

Your skin does not behave the same way in August as it does in January. Temperature, humidity, and UV intensity shift throughout the year, and each of these variables directly affects how your skin responds to glycolic acid. A routine that works perfectly in mild spring weather can cause irritation in dry winter air or increase hyperpigmentation risk during peak summer UV exposure. Yet almost no skincare guidance addresses this reality - most glycolic acid advice treats the routine as static, regardless of the calendar.

Seasonal adjustment is not about abandoning glycolic acid for months at a time. It is about making measured changes to concentration, frequency, and supporting products so that you maintain consistent results without overtaxing your skin barrier. The science behind these adjustments centers on three factors: ultraviolet radiation intensity, transepidermal water loss (TEWL), and barrier integrity - all of which vary significantly by season and climate [1].

Why Seasonal Adjustment Matters

Glycolic acid works by disrupting the bonds between corneocytes in the stratum corneum, accelerating cell turnover and allowing fresher skin to surface [2]. This mechanism does not change with the seasons - but the skin it acts upon does.

UV exposure changes everything. Glycolic acid increases the skin's sensitivity to ultraviolet radiation. Kornhauser et al. (2009) demonstrated that topical glycolic acid increases UV-induced erythema, DNA damage, and sunburn cell formation in human skin [1]. During summer months, when UV index values routinely exceed 8–10, this photosensitizing effect carries more practical risk than during winter months when the UV index may sit at 1–3. The same routine that poses minimal UV risk in December becomes a meaningful hyperpigmentation risk in July.

Humidity governs barrier function. The skin barrier performs differently at 80% relative humidity than at 20%. Research on seasonal TEWL variation shows that transepidermal water loss increases significantly during cold, dry months, indicating reduced barrier integrity [3]. When your barrier is already compromised by environmental dryness, adding glycolic acid - which temporarily disrupts barrier lipids - can push the skin past its tolerance threshold.

Temperature affects skin physiology. Cold exposure constricts blood vessels and slows cell turnover. Heat increases blood flow, sebum production, and product absorption. These physiological shifts mean the same concentration of glycolic acid is effectively stronger on warm, vasodilated skin than on cold, constricted skin.

Summer Adjustments

Summer presents the highest-stakes season for glycolic acid users. The combination of increased UV intensity, longer daylight hours, more time spent outdoors, and sweat-induced product migration creates a risk profile that demands deliberate adjustments.

The Core Risk: UV and Photosensitivity

The FDA requires all AHA-containing cosmetic products to carry a sunburn alert statement: "This product contains an alpha hydroxy acid (AHA) that may increase your skin's sensitivity to the sun and particularly the possibility of sunburn" [4]. This regulatory requirement exists because the research is unambiguous - AHAs increase photosensitivity, and glycolic acid is the most commonly used AHA in consumer products.

Kaidbey et al. (2003) found that four weeks of daily 10% glycolic acid reduced the minimal erythema dose (MED) by approximately 18% [5]. During summer, when baseline UV exposure is already elevated, this 18% reduction in the skin's natural UV defense becomes clinically significant. The practical consequence is a higher risk of sunburn, post-inflammatory hyperpigmentation, and accelerated photoaging - the exact outcomes that glycolic acid users are typically trying to prevent.

Summer Strategy

Reduce frequency. If you use glycolic acid daily in cooler months, consider dropping to every other day or 3 times per week during peak summer. This reduces cumulative photosensitization while maintaining exfoliation benefits.

Switch to PM-only use. If you have been using a glycolic acid cleanser or toner in the morning, move all acid use to your evening routine during summer. This maximizes the time between acid application and next-day UV exposure.

Consider reducing concentration. If you use a 10% serum year-round, stepping down to 7%–8% during June through August reduces photosensitivity while preserving most of the exfoliation benefit. For detailed guidance on selecting the right concentration, see our concentration guide.

Upgrade your sunscreen. Move from SPF 30 to SPF 50+ during summer if you have not already. Use a broad-spectrum formula and reapply every 2 hours during outdoor activity. Water-resistant formulas are essential if you sweat or swim.

Consider a gentler AHA. Mandelic acid and lactic acid are larger molecules with slower skin penetration and less photosensitizing potential. Some dermatologists recommend switching to these gentler AHAs during peak UV months, particularly for patients with Fitzpatrick skin types IV–VI who are at higher risk of post-inflammatory hyperpigmentation. If you are adjusting your routine for summer - swapping acids, adding new products, or changing application timing - use our ingredient interaction checker to verify that your seasonal combinations are safe.

Summer vs. Winter: Side-by-Side Comparison

Winter Adjustments

Winter introduces a different set of challenges. UV intensity drops (which is good), but humidity plummets - both outdoors and in heated indoor environments. This shift in moisture profoundly affects the skin barrier.

The Core Risk: Barrier Compromise and Dryness

Seasonal studies of transepidermal water loss consistently show that TEWL increases during winter months. Kikuchi et al. (2002) demonstrated significant seasonal variation in skin surface hydration and barrier function, with the lowest barrier integrity observed during cold, dry months [3]. When you apply glycolic acid to a barrier that is already weakened by environmental dehydration, the acid penetrates more aggressively and causes more irritation than it would on well-hydrated, barrier-intact skin.

The result is a common winter pattern: a glycolic acid routine that was comfortable in October suddenly causes redness, stinging, or flaking in January. The user assumes the product changed, but it is the skin's condition that shifted.

Winter Strategy

Add or upgrade your ceramide moisturizer. Ceramides, cholesterol, and free fatty acids are the three lipid classes that form the skin's natural barrier. A moisturizer containing these ingredients applied after glycolic acid provides immediate barrier support. This is the single most important winter adjustment.

Reduce frequency if flaking occurs. Mild dryness from glycolic acid is normal. Persistent flaking - especially flaking that does not resolve between applications - is a signal that the skin barrier cannot keep pace with the exfoliation rate. Drop from daily to every-other-day use, or from 5 times per week to 3 times.

Consider lower concentration. If you use 10% glycolic acid year-round and notice increased winter sensitivity, stepping down to 7%–8% during December through February can reduce irritation while maintaining results. You can calculate the difference in free acid delivery using our strength calculator.

Use a humidifier. Indoor heating drops relative humidity to 10%–30%, sometimes lower. A bedroom humidifier running overnight (targeting 40%–50% RH) directly combats the transepidermal water loss that weakens your barrier. This is one of the most effective and underutilized winter skincare interventions.

Apply glycolic acid to slightly damp skin with caution. Some sources recommend applying acids to damp skin for better absorption. In winter, this can backfire - increased penetration on a compromised barrier means increased irritation. Apply to clean, fully dry skin.

Humidity Effects on Glycolic Acid Performance

Humidity is the most underappreciated variable in glycolic acid skincare. It affects the skin barrier, product absorption, and irritation potential more directly than temperature alone.

High Humidity (Above 60% RH)

In humid environments, the skin retains moisture more effectively. TEWL decreases because the humidity gradient between the skin surface and the surrounding air is smaller. The stratum corneum stays better hydrated, the barrier lipid structure is more intact, and the skin is generally more resilient.

For glycolic acid users, high humidity is favorable. The skin tolerates acids better when its barrier is intact. Products spread more evenly on hydrated skin, and the risk of localized irritation from uneven product distribution (pooling in dry patches) is lower. People living in tropical and subtropical climates often find they can comfortably use higher concentrations or more frequent applications compared to people in dry climates.

Low Humidity (Below 30% RH)

Low humidity is the more common problem. It occurs in desert climates year-round, in heated buildings during winter, in air-conditioned environments during summer, and in airplane cabins. Research demonstrates that low ambient humidity increases TEWL and reduces stratum corneum hydration, leading to impaired barrier function [6].

When humidity is low, glycolic acid encounters skin that is already partially compromised. The acid's normal mechanism - disrupting corneocyte bonds in the stratum corneum - operates on a barrier that has less structural integrity to begin with. The result is greater effective penetration and more irritation at the same concentration and frequency.

Practical takeaway: If you split time between a humid environment and a dry one (for example, living in a humid city but working in an aggressively air-conditioned office), your skin barrier fluctuates throughout the day. Apply glycolic acid in the evening after spending time in more humid conditions (or after running a humidifier), rather than immediately after hours in dry air conditioning.

Travel Considerations

Travel introduces rapid environmental changes that your skin has no time to acclimate to. A person flying from Seattle to Dubai shifts from temperate, moderate humidity to desert heat and intense UV within hours. Your glycolic acid routine needs to account for these sudden transitions.

Flying

Commercial aircraft cabins maintain humidity levels of approximately 10%–20% - lower than most deserts [7]. On a long-haul flight, this extreme dryness measurably increases TEWL and reduces skin hydration. If you apply glycolic acid the evening before a flight, your skin enters this dehydrating environment with a freshly exfoliated, slightly more vulnerable barrier.

Recommendations for flights:

• Skip glycolic acid the night before and the night of a long flight (anything over 4 hours)
• Apply a heavy ceramide moisturizer before boarding
• Use a hydrating mist during the flight to combat surface dehydration
• Resume glycolic acid 24 hours after arrival, once your skin has rehydrated

Tropical Vacations

Tropical destinations combine intense UV (often UV index 10+), high humidity, and extended outdoor time. The humidity is skin-friendly, but the UV intensity makes glycolic acid use higher-risk.

Recommendations for tropical travel:

• Reduce glycolic acid to 2–3 times per week
• Use SPF 50+ broad-spectrum sunscreen, reapply every 90 minutes during outdoor activity
• Avoid glycolic acid entirely on days with extended beach or pool time
• Resume your normal routine after returning home

Cold-Climate Destinations

Traveling to cold, dry destinations (ski trips, Nordic countries in winter) presents the opposite challenge. Extreme cold, low humidity, and wind exposure damage the barrier rapidly.

Recommendations for cold-climate travel:

• Reduce glycolic acid frequency or pause entirely for trips under a week
• Bring a rich ceramide moisturizer and apply liberally
• Consider a facial oil or occlusive balm as a final protective layer
• Resume normal frequency 2–3 days after returning to your home climate

Altitude

UV radiation intensity increases approximately 10%–12% for every 1,000 meters of elevation gain [8]. A ski resort at 3,000 meters receives roughly 30%–36% more UV radiation than sea level. Combined with snow reflection (which can nearly double UV exposure on the face), high altitude creates exceptional photosensitivity risk for glycolic acid users.

Recommendations for altitude:

• SPF 50+ is the minimum, not the recommendation
• Reduce glycolic acid frequency significantly during mountain stays
• Reapply sunscreen every 60–90 minutes during outdoor activity at elevation
• Wear a hat and sunglasses for physical UV protection

Climate-Specific Recommendations

Tropical/Humid Climates

If you live in a consistently tropical environment (Southeast Asia, Central America, equatorial regions), your skin barrier benefits from constant high humidity, but you face year-round high UV. The strategy is straightforward: moderate glycolic acid frequency (3–5 times per week), PM-only application, and unwavering SPF 50+ use every morning. Your skin will likely tolerate higher concentrations than someone in a dry climate, but the UV risk never drops.

Desert/Arid Climates

Desert residents face low humidity year-round. The barrier is under constant dehydrative stress. Use glycolic acid conservatively - start with lower concentrations and lower frequency than general guidelines suggest. A ceramide-rich moisturizer is essential, not optional. A humidifier in the bedroom is strongly recommended. Despite clear skies, UV intensity in desert environments is high, so sunscreen compliance is critical.

Temperate/Four-Season Climates

Temperate climates offer the widest range of conditions across the year. Use the summer and winter strategies outlined above, with transitional adjustments in spring and autumn. Spring (March through May in the Northern Hemisphere) is when UV begins increasing - this is the time to start dialing back frequency or concentration. Autumn (September through November) is when UV decreases and you can gradually increase your glycolic acid use again.

Cold/Sub-Arctic Climates

Extreme cold climates (Scandinavia, northern Canada, Russia) combine very low temperatures, very low humidity, and strong winds. The skin barrier is under heavy stress for 6–8 months of the year. Glycolic acid use should be conservative during these months: 2–3 times per week at moderate concentrations, always paired with heavy barrier-repair moisturizers. During the brief summer, when temperatures and humidity rise, you can increase frequency. UV exposure during sub-arctic summers can be surprisingly high due to long daylight hours, so sunscreen remains important.

Year-Round Constants

Regardless of season, climate, or travel plans, three principles never change for glycolic acid users.

Sunscreen every single day. UV radiation penetrates clouds. It reflects off snow, water, and concrete. It reaches you through windows. If you use glycolic acid at any frequency, SPF 30+ broad-spectrum sunscreen is non-negotiable every morning, 365 days per year. No seasonal adjustment changes this. The photosensitizing effect of glycolic acid persists for approximately one week after your last application [5], so even a temporary break from the acid does not eliminate the need for sun protection. For more on why this matters, see our guide on side effects and safety.

Moisturizer every single day. Glycolic acid increases TEWL temporarily after application. A moisturizer applied after the acid helps restore barrier lipids and prevent dehydration. In humid summers you can use a lightweight gel. In dry winters you may need a heavy cream. But the step itself is never optional.

Listen to your skin. Persistent redness, stinging, flaking, or increased sensitivity are signals to reduce frequency or concentration - regardless of what the calendar says. Your skin's real-time feedback overrides any seasonal schedule. If your skin is telling you that your current routine is too much, scale back. You can always increase again when conditions change. For more on recognizing and managing irritation, see our side effects guide.

Frequently Asked Questions

Should I stop using glycolic acid entirely in summer?

No. Stopping glycolic acid for three months means losing the cumulative benefits - improved texture, reduced hyperpigmentation, and increased cell turnover - that took weeks to build. Instead, reduce frequency (from daily to 3–4 times per week), ensure PM-only application, and upgrade to SPF 50+ sunscreen. If you are spending all day at the beach, skip the acid that day. But a blanket summer hiatus is unnecessary for most people. If your skin is dark (Fitzpatrick IV–VI) and you have a history of post-inflammatory hyperpigmentation, consult a dermatologist about whether a temporary switch to a gentler exfoliant is appropriate. For more on building a sustainable routine, see our routine guide.

How do I know if winter dryness is from glycolic acid or just from the weather?

The distinction matters because the solutions differ. If the dryness is purely environmental (low humidity), adding a richer moisturizer and running a humidifier should resolve it. If glycolic acid is the primary cause, you will notice that dryness and flaking are worse on the mornings after acid application and better on off-days. The test is simple: skip glycolic acid for one week while maintaining your moisturizer and humidifier. If the dryness resolves, the acid was contributing. Resume at lower frequency (every other day instead of daily) and reassess. Understanding how pH and concentration interact can also help you choose a winter-appropriate product.

Can I use glycolic acid on a plane?

It is technically possible but inadvisable. The cabin environment (10%–20% humidity) puts the skin barrier under significant stress. Applying an exfoliating acid in this context increases irritation risk with no practical benefit. If you want to maintain your routine during travel, apply glycolic acid the evening before departure (assuming it is not a red-eye), skip it during travel, and resume at your destination once your skin has had 12–24 hours to rehydrate. Use the flight time for hydration (ceramide moisturizer, hyaluronic acid serum, hydrating mist) rather than active treatment.

References

1. 1. Kornhauser A, Wei RR, Yamaguchi Y, et al. (2009). The effects of topically applied glycolic acid and salicylic acid on ultraviolet radiation-induced erythema, DNA damage and sunburn cell formation in human skin. J Dermatol Sciclinical trial
2. 2. Fartasch M, Teal J, Menon GK (1997). Mode of action of glycolic acid on human stratum corneum: ultrastructural and functional evaluation of the epidermal barrier. Arch Dermatol Resin vitro study
3. 3. Kikuchi K, Kobayashi H, Le Fur I, et al. (2002). Seasonal changes in skin surface condition and the relation to environmental factors. Skin Res Technolobservational study
4. 4. U.S. Food and Drug Administration (2022). Alpha Hydroxy Acids in Cosmetic Products. FDA Consumer Advisoryregulatory guidance
5. 5. Kaidbey K, Sutherland B, Bennett P, et al. (2003). Topical glycolic acid enhances photodamage by ultraviolet light. Photodermatol Photoimmunol PhotomedRCT
6. 6. Sato J, Yanai M, Hirao T, Denda M (2002). Transepidermal water loss and skin hydration in relation to ambient humidity. Exog Dermatolexperimental study
7. 7. Patel T, Turrentine JE, Engasser HG, et al. (2015). Air travel and skin health: a review of dermatologic concerns related to commercial flights. J Am Acad Dermatolreview
8. 8. Moehrle M (2008). Ultraviolet radiation and the athlete: risk, sun safety, and barriers to implementation. Br J Sports Medreview

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