[Pre-Rainy Season Survey] 'Maskne' and 'Chest Acne' Spike at Over 70% Humidity; 82.7% Report Skin Troubles During Rainy Season

Key Findings of the Survey

In conclusion, the increase in acne during the rainy season is mainly caused by increased sebum secretion due to rising humidity, and the tendency for sweat and sebum to clog pores. The key to skincare in high-humidity periods is not to 'increase cleansing power,' but to 'remove excess sebum while maintaining hydration.' For torso acne on the chest or back, it is important to distinguish it from folliculitis, and a visit to a dermatologist is recommended if symptoms do not improve after two weeks.

- 82.7% have experienced skin troubles during the rainy season, with 67.3% noting the worsening of acne/breakouts. - 78.4% of mask wearers have experienced 'maskne,' with the risk of onset 2.1 times higher at humidity levels of 70% or above. - While torso acne (chest/back) increases 1.8 times during the rainy season, 61.5% do not know the appropriate care methods.

Terminology

### Rainy Season-Type Skin Troubles This is a collective term for skin diseases that easily occur in high-humidity environments (above 70%). Factors such as increased sebum secretion, pore occlusion due to sweat, and promoted bacterial growth act in combination to cause acne, breakouts, prickly heat, and eczema. It is characterized by an increase in patient numbers during the rainy season, particularly from June to July.

### Maskne (Mask Acne) This refers to acne caused by friction, stuffiness, and bacterial growth due to wearing a mask. The humidity inside a mask becomes 20-30% higher than outside air, making it easier for sebum and sweat to clog pores. It frequently occurs around the chin, cheeks, and nose, and has been drawing attention as a skin problem that has increased sharply since 2020.

### Torso Acne (Chest/Back Acne) This is a collective term for acne that occurs on the chest and back. Unlike facial acne, differentiation from folliculitis and Malassezia folliculitis is important, and there are many cases that do not improve with standard acne medications. Due to being an area with high sweat and sebum secretion and stuffiness from clothing, it tends to worsen in high-humidity environments.

Comparison of Facial and Torso Acne

| Comparison Item | Facial Acne | Torso Acne (Chest/Back) | | --- | --- | --- | | Main Causative Bacteria | Cutibacterium acnes | C. acnes or Malassezia | | Predominant Areas | T-zone, cheeks, chin | Center of chest, between shoulder blades | | Worsening Factors | Sebum, makeup, stress | Stuffiness from clothes, sweat, friction | | Efficacy of Self-care | Relatively high | Depends on the bacteria | | Recommendation to Consult | If no improvement after 2 weeks | If no improvement after 2 weeks | | Estimated Treatment Duration | 2-3 months | 1-3 months |

*General estimates; individual results may vary.

The Tetsu-Ketsukai Medical Corporation, which operates aesthetic dermatology and dermatological surgery clinics nationwide (Shinjuku, Shibuya, Ueno, Ikebukuro, Tokyo, and Omiya branches), conducted this survey in May 2026, just before the start of the rainy season, targeting 300 men and women across the country.

Survey Overview Target: Men and women across the country aged 20-50 who have struggled with acne/breakouts in the past year. Duration: May 18, 2026 - May 27, 2026 Method: Internet survey Number of participants: 300

Survey Results - 82.7% have experienced skin troubles during the rainy season, realizing the correlation with humidity. - More than 80% feel the increase in skin troubles, revealing the significant impact of high humidity. Those who answered 'clearly increases' (45.3%) tend to be conscious of preventative skincare before the rainy season every year. - 67.3% consider the worsening of acne and breakouts to be the most serious issue. - 78.4% have experienced 'maskne.'