What is the post-sun rebound effect, and how can you prepare for it?

The rebound effect of sun exposure and acne

Have you noticed that your skin looks betterin the summer? It becomes smoother and clearer. Pimples fade away, as if the sun had cured your acne. However, the joy is short-lived... When school starts again, blemishes come back with a vengeance. This is what’s known asthe post-sunrebound effect. It’s a common phenomenon, but one you can avoid with a few good habits, starting right from the first days of summer. We’ll explain everything.

The Sun: Acne’s False Friend

It’s commonly believed that the sun “cures” pimples… But that’s a myth. In reality, acne and the sun don’t mix very well...

In France, the intensity of solar radiation is 4 to 9 times higher in summer than in winter. To protect itself from the summer sun—and especially from the UV rays it emits—the skin thickens and the pores temporarily tighten. This is a natural defense mechanism called hyperkeratinization.

However, this thickening of the skin has a downside: sebum has a harder time flowing out, and the pores become clogged. And that’s how blemishes end up “trapped” and hidden beneath the skin’s surface.

The result: during the summer, with the sun’s intense rays, acne is rare. The skin looks clearer and smoother. But this is only on the surface, because blemishes are actually just waiting for one thing: to break out!

When school starts again, it’s usually a disaster: pimples, blackheads, and microcysts come back in full force. This sudden resurgence of blemishes is calledthe rebound effect.

What exactly is the rebound effect?

By the end of summer, the skin returns to its normal thickness and the pores reopen. That’s when acne breakouts, blackheads, and microcysts—which have been “trapped” beneath the skin all summer—suddenly resurface.

That’s why we talk about the rebound effect: after a lull—once sun exposure has ended—skin imperfections reappear as early as the first few days of September… and often even more intensely than before.

The rebound effect primarily affects:

Combination to oily skin.
Acne-prone skin.
People who stopped their anti-breakout routine over the summer (mistakenly thinking that the sun had cleared up their acne…).
People who were exposed to the sun without adequate sun protection and/or who did not properly cleanse their skin during the summer.

How can you anticipate and avoid the post-summer rebound effect?

You don't need to completely overhaul your routine to avoid the rebound effect! The key is to prevent the skin from thickening due to sun exposure and to stop bacteria from multiplying. To do this, here are a few tips to follow starting at the beginning of summer.

Don't stop your routine, especially if it's designed to fight acne

Don't fall into the trap of stopping your skincare routine or your anti-breakout treatments just because the sun makes it seem like your acne is getting better. That will only set the stage for a rebound effect. Keep taking care of your skin all summer long, consistently.

On the other hand, if your usual skincare routine includes products containing photosensitizing ingredients (retinol, AHAs, BHAs, benzoyl peroxide, or certain essential oils), it is indeed recommended that you stop using them—or at least limit their use—during the summer.

Cleanse thoroughly every morning and evening

When it’s really hot, it’s tempting to just splash your face with cold water. But between sweat, sebum, sunscreen, salt, chlorine, and sand clogging your pores… In the summer, your skin actually needs a particularly thorough cleansing.

Thoroughly cleanse your skin twice a day, in the morning and at night, with a gentle cleanser: Dermo-Purifying Gel Cleanser if you have combination, oily, or acne-prone skin, Gentle Cleansing Foam or Cleansing Micellar Water.

Gently exfoliate at least once a week

Once or twice a week, be sure to exfoliate your skin to prevent it from becoming thickened, remove dead skin cells, and clear your pores of sebum and accumulated impurities.

However, avoid exfoliating right before sun exposure, as well as scrubs that are too frequent, too abrasive, or too drying, as these could have the opposite effect and make your skin more sensitive to the sun. Opt for:

A fine-grained mechanical scrub such as the Gentle Scrub, unless you have pimples.
If you have acne, use an enzyme scrub instead. The Purifying Radiance Mask, for example, contains enzymes that gently exfoliate.

Moisturize your skin, even (and especially) if it's shiny

In the summer heat, your skin can quickly become dehydrated. Even if your skin is oily or shiny, that doesn’t mean it’s sufficiently hydrated. On the contrary: it’s probably a sign that it’s dehydrated and is trying to compensate for the lack of water by producing more sebum. However, this excess sebum can build up under the skin and clog your pores.

To prevent excess sebum production caused by dehydration, be sure to moisturize your skin daily, ideally in the morning and at night:

If you have oily skin, opt for a lightweight, non-comedogenic moisturizer—especially during the day—such as the Matifying and Unifying Fluid , which also helps reduce shine.
Otherwise, a cream with a melt-in texture containing active ingredients such ashyaluronic acid, aloe vera, or glycerin will work perfectly: the Hydra Intense Cream , for example.

Protect your skin from the sun every day

The ultimate way to prevent the rebound effect? Good sun protection. In fact, if the skin is properly protected from the sun’s UV rays, it won’t need to thicken.

Every morning, as the final step in your skincare routine, apply a broad-spectrum (UVA and UVB protection) sunscreen with an SPF of at least 50, such as the Invisible Cream. Reapply every 2–3 hours during prolonged sun exposure, and after swimming or sweating.

Limit your makeup

In the summer, your skin sweats a lot. If you apply heavy makeup on top of that, it can “trap” sweat and sebum and clog your pores.

It's not necessarily about avoiding makeup altogether, but:

To go bare-skinned whenever possible (vacations, weekends, working from home, etc.).
Opt for lightweight, non-comedogenic formulas (Tinted Cream SPF 50+, BB cream…).

And if you decide to wear makeup, don't forget to use makeup remover!

The bottom line: To prevent pimples from coming back when school starts, it's better to be safe than sorry.

Your skin looks better in the summer, but the truth is that sun exposure and acne don’t mix very well. The good news? A rebound effect isn’t inevitable. By taking the right steps from the start of summer, you can prevent it—or at least significantly limit it. To do so:

Don't skip your routine—keep taking care of your skin even if it seems to be doing fine.
Cleanse and moisturize your skin every day, morning and night.
Gently exfoliate 1 to 2 times a week.
Protect yourself from the sun every day with a high SPF sunscreen that blocks UVA and UVB rays.
Choose a light formula over heavy coverage makeup.