Acne and Sun Exposure: Effects and Recommended Actions

Introduction¹

Sun exposure is sometimes regarded as beneficial for acne-prone skin due to its temporary drying effect on lesions and apparent reduction in inflammation. However, this perception is misleading, as ultraviolet rays, especially UVB, can worsen acne lesions and damage skin health over the long term.

Given these complex and harmful effects of the sun on acne, dermatologists advise tailored photoprotection. Adopting fundamental sun-safety measures and using a broad-spectrum sunscreen specifically formulated for acne-prone skin helps shield the skin without clogging pores or triggering new breakouts. Protecting yourself from the sun’s adverse effects not only prevents acne flare-ups but also minimises overall sun-related risks to the skin.

The Effects of Sunlight on Acne-Prone Skin¹

The Contradictory Effects of Sun Exposure on Acne

Ultraviolet rays may have a drying effect on sebum production and acne lesions, which is why sun exposure is often mistakenly thought to be beneficial for acne. In reality, individual responses vary while some people notice a reduction in inflammatory lesions during summer months, others experience a worsening of symptoms. Indeed, studies have found that 40–50% of acne sufferers see their condition deteriorate in summer.

Differences between UVA, UVB and Their Impact on Acne

Ultraviolet radiation affects acne in different ways:

• UVA and visible light: UVA1 rays, alongside visible light, can reduce inflammation and decrease colonisation by Cutibacterium acnes, without increasing sebum production or inflammation.
• In reverse, UVB rays tend to increase pro-inflammatory molecules, stimulate keratinocyte proliferation (the cells that form the epidermis), and increase sebum production. These changes encourage pore blockage and trigger or exacerbate acne

Post-Inflammatory Hyperpigmentation

In individuals with darker skin tones, inflammatory acne lesions exposed to the sun can lead to post-inflammatory hyperpigmentation, a darkening of the skin caused by inflammation resulting from excess melanin production and redistribution in the epidermis. Visible light further stimulates melanin production in the upper layers of the skin, accentuating blemish marks.

Post-Inflammatory Erythema

Sun exposure can also induce post-inflammatory erythema, particularly in fair-skinned people. This appears as persistent redness due to capillary dilation in the affected area.

Risks of Tanning Beds

Using tanning beds, sometimes employed as a form of self-treatment for acne, carries significant risks, including premature skin ageing, worsening of post-inflammatory hyperpigmentation, and increased skin cancer risk. Dermatologists recommend avoiding them.

Choosing the Right Sunscreen Products for Acne-Prone Skin¹

Benefits of Sunscreen for Acne-Prone Skin

Sunscreens do more than blocking UV rays. They also:

• Hydrate the stratum corneum and strengthen the skin barrier.
• Protect the skin from pollution.
• Offer potential sebum-regulating, depigmenting, anti-inflammatory or antioxidant properties.
   

Selecting a Suitable Sunscreen

Opt for sunscreens with the following features:

• Broad-spectrum (UVA/UVB) with SPF ≥ 30: effective defense against the sun’s harmful effects.
• Lightweight, water-based texture: for a pleasant, non-greasy application.
• Fast absorption and a mattifying effect: reduces shine and suits oily skin.
• Non-comedogenic: to avoid blocking pores and prevent new lesions.

Advantages of Tinted Sunscreens for Acne-Prone Skin

Tinted sunscreens are especially beneficial for those prone to post-inflammatory hyperpigmentation and for darker skin tones. Pigments such as titanium dioxide and iron oxides:

• Shield against visible light and UVA1, which contribute to post- inflammatory hyperpigmentation.
• Provide a camouflage effect that conceals imperfections and helps mitigate the emotional impact of acne, such as reduced self-esteem.

Additional Measures to Prevent UV-Related Damage^{2 3}

Understanding the UV Index and Adjusting Protection

The UV index measures the intensity of solar radiation. Checking this index to adapt your protection is essential, especially during peak exposure periods (May to August in Europe). Depending on the index, which ranges from low to extreme, several precautions can help limit skin damage.

Seek Shade and Limit Exposure

To minimise sun exposure, stay in the shade whenever possible, especially between 12 PM and 4 PM when UV radiation is at its peak. Limit the duration of direct exposure to allow the skin to regenerate its defences, and avoid high-risk situations such as intense reflections off snow, sand or water.

Wear Protective Clothing

Choose dark-coloured, covering garments to block UV rays effectively. UV-protective clothing (UPF-rated) is recommended, and dry fabrics shield better than wet ones. Opt for long-sleeved shirts and trousers, especially during prolonged outdoor activities.

Wear UV-Filtered Sunglasses

UV-certified sunglasses protect both the eyes and the delicate skin around them. Wraparound styles or wide frames offer enhanced coverage and further reduce UV exposure.

Choose a Wide-Brimmed Hat

A wide-brimmed hat effectively shields the face, neck and ears. Avoid straw hats with holes that let UV rays through; instead, choose thick, woven materials for optimal protection.

Risks Associated with Acne Treatments

Acne therapies can increase sun sensitivity, which raises the risk of sunburn, irritation, and hyperpigmentation.

Understanding Photosensitising Medications⁴

In dermatology, drug-induced photosensitivity refers to skin reactions caused by photosensitising medications that heighten sun sensitivity. Two types of responses occur: phototoxicity and photoallergy.

• Phototoxicity may trigger an intense, painful sunburn, sometimes with blisters, within hours of minimal sun exposure. It affects exposed areas: topical treatments induce reactions at the application site, whereas oral medications can sensitise all sun-exposed skin. The severity correlates with sun intensity, especially on fair skin. This sensitivity fades gradually with sun avoidance or, if advised by a physician, upon stopping the medication.
• Photoallergy, less common than phototoxicity, is a proper allergic reaction in individuals who are predisposed. It emerges 5–21 days after initial drug exposure and requires at least one week of sun exposure to sensitise the body. Thereafter, even minimal sunlight can provoke eczematous or urticarial lesions that may extend to non-exposed areas. Unlike phototoxicity, photoallergic eruptions can persist long after discontinuing the drug.

Main Acne Treatments with Photosensitising Effects

Topical treatments¹ ² ⁴

Topical retinoids increase cell turnover and may thin the stratum corneum, making the skin more susceptible to UV damage.
Benzoyl peroxide is an antimicrobial that can dry out the skin and increase sensitivity to UV rays.
Topical antibiotics, particularly tetracyclines, heighten sun sensitivity.

Oral treatment¹ ² ⁴

Oral antibiotics (doxycycline, minocycline, and lymecycline) are photosensitising and increase the risk of phototoxic reactions.
Oral retinoids (isotretinoin), used for severe acne, can make the skin and lips extremely sensitive to UV radiation. Rigorous photoprotection is advised throughout treatment.

In-Clinic Dermatological Procedures¹ 

Patients undergoing chemical peels, microdermabrasion or laser therapies, particularly for acne scar management, must maintain strict photoprotection to optimise healing and prevent post-inflammatory hyperpigmentation. Tinted sunscreens are highly recommended here for their protective qualities and ability to conceal redness.