In our everyday lives, we often encounter situations that remind us of the delicate dance between temperature and physical matter.
Have you ever noticed that a metal lid can be particularly stubborn to open after a meal? Or perhaps you’ve felt the smoothness of a wooden chair becoming less inviting on a hot summer day? These seemingly simple experiences are reflections of a fascinating phenomenon known as thermal expansion.
Thermal expansion is the tendency of matter to change its shape, area, and volume in response to a change in temperature.
Retinoids are vitamin A derivatives widely used in dermatology to treat acne because of their ability to regulate follicular keratinization, a key biological process involved in clogged pores and comedone formation. In acne-prone skin, keratinocytes lining the hair follicle shed irregularly and adhere to one another instead of dispersing evenly. This abnormal cohesion leads to the formation of microcomedones, the earliest microscopic lesions in acne. Retinoids work at the cellular level by binding to retinoic acid receptors within keratinocytes, influencing gene expression that governs cell differentiation and turnover. By promoting more orderly shedding of cells and reducing their tendency to clump together, retinoids help keep the follicular canal clear.
When follicular keratinization becomes more regulated, the buildup of sebum and dead skin cells inside pores is less likely to form compact plugs. This effect is particularly important in preventing blackheads and whiteheads, collectively known as comedonal acne. Unlike treatments that primarily target surface oil, retinoids address the upstream mechanism that initiates pore blockage. Over time, consistent use may reduce the number of existing comedones and help prevent new lesions from forming. Because acne begins microscopically weeks before becoming visible, retinoids are often considered foundational in long-term acne management.
Retinoids may also indirectly influence other contributors to acne. By normalizing the follicular environment, they can make conditions less favorable for the proliferation of Cutibacterium acnes, which is involved in inflammatory lesions. Some retinoids also demonstrate mild anti-inflammatory properties, which may help reduce redness associated with breakouts. Additionally, improved cell turnover can enhance the penetration and effectiveness of complementary ingredients such as benzoyl peroxide or topical antibiotics when prescribed in combination therapy.
Several forms of retinoids are used in skincare and dermatology. Over-the-counter adapalene is commonly recommended for mild to moderate acne because it selectively binds to specific retinoic acid receptors and is generally well tolerated. Prescription options such as tretinoin or tazarotene may be considered for more persistent or severe cases under medical supervision. Regardless of the specific formulation, gradual introduction is often advised to minimize irritation. Temporary dryness, peeling, or mild redness may occur as the skin adjusts, particularly during the first several weeks.
Because retinoids increase cell turnover, they can initially bring underlying microcomedones to the surface, a process sometimes referred to as purging. This phase is typically temporary and differs from irritation-induced breakouts. Supporting the skin barrier with a gentle cleanser, non-comedogenic moisturizer containing ceramides, and daily sunscreen is important, as retinoids can increase photosensitivity. Harsh scrubbing or combining too many active ingredients at once may worsen irritation and compromise adherence to treatment.
Improvements in comedonal acne generally become noticeable after several weeks to a few months of consistent use, reflecting the natural pace of skin renewal. While retinoids are highly effective in regulating follicular keratinization, they do not permanently alter sebaceous gland activity, so maintenance therapy is often necessary to sustain results. Individuals with persistent, severe, or scarring acne should consult a qualified dermatologist to determine the most appropriate retinoid regimen and ensure safe, evidence-based care .
