Summer Skin Troubles Caused by 'Air-Conditioner Dryness'! Survey Reveals Shocking Reality — Dermatologist Explains Solutions for 'Inner Dryness' Experienced by Over 80%

【Conclusion】Key Findings of This Survey

In conclusion, the primary causes of tight, dry skin during summer are 'dry air from air conditioning' and 'a weakened skin barrier due to excessive sebum production'. 'Inner dryness' refers to a condition where the skin surface feels oily due to sebum, yet the inner layers (stratum corneum) are dehydrated—a condition rapidly increasing among modern individuals who spend long hours in air-conditioned environments. Effective countermeasures include using lightweight yet highly moisturizing toners and lotions together, utilizing humidifiers, and maintaining regular hydration.

・73.7% responded that they 'feel tightness or dryness in their skin during summer'

・Only 26.3% correctly understand the true meaning of 'inner dryness'

・84.0% spend 6 or more hours per day in air-conditioned environments

Terminology Explanation

What is Inner Dryness?

Inner dryness refers to a condition where, despite an oily surface due to sebum, the skin's interior (stratum corneum) lacks sufficient moisture. Because the skin appears oily, dryness is often overlooked, and incorrect skincare routines—such as over-cleansing or insufficient moisturizing—can worsen the condition.

What is Skin Barrier Function?

The skin barrier function refers to the outermost layer of the skin (stratum corneum) protecting against external irritants and preventing internal moisture loss. This function is maintained by intercellular lipids (such as ceramides) and natural moisturizing factors (NMF), and can easily deteriorate due to dryness or UV exposure.

What is Transepidermal Water Loss (TEWL)?

Transepidermal Water Loss (TEWL) measures the amount of water evaporating from the skin's surface and is used as an indicator of skin barrier function. Higher TEWL values indicate greater moisture evaporation from the skin, signaling a weakened barrier function.

Comparison of Summer Moisturizing Methods

Comparison Item

Lightweight Type Only

Lightweight + Lotion Combination

High-Moisture Type

Moisture Retention Duration

1–2 hours

3–4 hours

5–6 hours

Greasy Feeling

Almost none

Slight

Noticeable

Effectiveness in Improving Inner Dryness

Low

Medium to High

High

Suitability in Air-Conditioned Environments

Insufficient

Appropriate

Slightly Heavy

Recommended Skin Type

Oily Skin

Combination/Inner Dry Skin

Dry Skin

Recommended Reapplication Frequency

3–4 times

2 times

1–2 times

*General guidelines; individual results may vary.

IC Clinic (Shinjuku, Shibuya, Ueno, Ikebukuro, Tokyo, and Omiya branches), operated by the Medical Corporation Tekiketsukai, conducted a real-world survey on summer skin issues, revealing the serious reality of 'inner dryness (hidden dryness)' in air-conditioned environments. The clinic specializes in dermatology and plastic surgery, and aims to promote accurate skincare knowledge through these survey findings.

Survey Background

In recent years, with the rise of office and remote work, more people are spending extended periods in air-conditioned indoor spaces. While summer is often associated with sweaty, oily skin, there has been a sharp increase in individuals suffering from 'inner dryness'—where skin moisture is depleted due to dry indoor air from air conditioning. However, many fail to recognize dryness due to surface oiliness and continue with incorrect skincare. Therefore, our clinic conducted this survey to assess awareness and real-life experiences regarding summer skin dryness and to promote proper countermeasures.

Survey Overview

Target: Men and women aged 20–50 across Japan who regularly spend time in air-conditioned environments

Survey Period: June 15–24, 2026

Method: Online survey

Number of Respondents: 300

Survey Results 【Result】Over 70% Experience Skin Dryness Even in Summer

Question: Do you feel tightness or dryness in your skin during summer (June–August)?

Combining 'often feel' and 'sometimes feel,' 73.7% reported experiencing dryness, revealing that a majority still face dry skin issues in summer. Although increased sweat and sebum may suggest no dryness, over half are actually aware of dryness symptoms.

【Result】Only 1 in 4 Understands the Correct Meaning

Question: Do you know the meaning of the term 'inner dryness'?

41.7% responded 'I've heard of it but the meaning is unclear,' while only 26.3% correctly understood the term. While awareness is growing, accurate understanding has not kept pace.

【Result】Over 80% Spend 6+ Hours Daily in Air-Conditioned Environments

Question: How many hours per day do you spend in air-conditioned environments?

84.0% spend 6 or more hours daily in such environments. Notably, 38.7% spend '10 hours or more,' highlighting that most modern individuals are exposed to dry air for prolonged periods.

【Result】Nearly 40% Use Only 'Lightweight' Products, Risking Insufficient Moisture

Question: What moisturizing measures do you take in summer? (Multiple answers allowed; select the most important)

'Only lightweight toner' was the top response at 37.3%, and combined with 'no particular moisturizing care' at 14.7%, over half may lack adequate moisturizing routines. Avoiding moisturizers due to summer oiliness appears to be worsening inner dryness.

【Result】'Shininess and Oiliness' Top Complaint, Yet May Stem from Dryness

Question: What summer skin issue troubles you most?

'Shininess and oiliness' was the top concern at 31.7%, likely due to the skin overproducing sebum to compensate for internal dehydration in an inner dry state. 'Enlarged pores' and 'skin irritation' are also linked to a weakened barrier from dryness, suggesting the top three concerns may all relate to inner dryness.

Survey Summary

This survey revealed that over 70% experience skin dryness in summer, primarily due to spending over 6 hours daily in air-conditioned environments. Meanwhile, only 1 in 4 correctly understands inner dryness, and over half may lack proper moisturizing care due to avoiding it for fear of oiliness. The underlying cause of common summer skin issues—shine, pores, and irritation—may actually be hidden inner dryness, underscoring the importance of science-based skincare.

Doctor's Comment | Dr. Kouta Takakura, IC Clinic

With over 15 years of clinical experience in dermatology, I can say that most summer skin issues stem from 'invisible dryness,' specifically inner dryness. It's crucial to look beyond surface oiliness and focus on maintaining internal skin hydration.

Dry air from air conditioning can damage skin more than winter outdoor air. In winter, people are aware of dryness and prioritize moisturizing, but in summer, the oily feel from sweat and sebum often leads to the misconception that 'moisturizing isn't needed.' However, air conditioner dehumidifying functions can easily lower indoor humidity below 40%.

The stratum corneum, responsible for skin barrier function, only operates properly when adequately hydrated. In air-conditioned environments, transepidermal water loss (TEWL) increases, depleting moisture from the stratum corneum. In response, the skin produces excess sebum