When we think about the world around us, it’s easy to overlook the invisible processes that are constantly at work.
From the rust forming on a bicycle left out in the rain to the delightful scent of freshly baked bread, chemical reactions are happening all around us, shaping our experiences and the environment.
But what exactly are these reactions, and how can we understand them better? Let’s take a gentle journey into the world of chemistry, uncovering the beauty and simplicity of chemical reactions, step by step.
Post-inflammatory hyperpigmentation, often abbreviated as PIH, is a common consequence of acne-related inflammation. It develops when inflammatory processes within the skin stimulate melanocytes to produce excess melanin in response to injury. Acne lesions, particularly inflamed papules, pustules, or nodules, trigger the release of cytokines and other mediators that can increase pigment production. When the lesion heals, it may leave behind a flat brown, tan, or grayish mark at the site of previous inflammation. Unlike acne scars, which involve structural changes in the skin, post-inflammatory hyperpigmentation reflects altered pigment distribution rather than permanent tissue damage.
The risk and severity of PIH are influenced by multiple factors, including skin tone and the intensity of inflammation. Individuals with medium to deeper skin tones often have more active melanocytes and may be more prone to developing noticeable hyperpigmentation after breakouts. Picking or squeezing acne lesions can worsen inflammation and increase the likelihood of persistent discoloration. Delayed or inadequate treatment of inflammatory acne may also allow deeper inflammatory responses that heighten pigment stimulation.
Because post-inflammatory hyperpigmentation is triggered by inflammation, controlling acne activity is a foundational step in prevention. Topical retinoids such as adapalene or tretinoin help normalize follicular keratinization, reduce microcomedone formation, and may gradually improve uneven pigmentation over time by increasing cell turnover. Azelaic acid is often used because it can help reduce both acne lesions and excess pigment production. Niacinamide may support barrier function while also helping improve the appearance of uneven skin tone. Chemical exfoliants such as salicylic acid or alpha hydroxy acids can assist with surface cell turnover, although they should be introduced gradually to avoid irritation that could worsen discoloration.
Sun exposure significantly influences the persistence of hyperpigmentation. Ultraviolet radiation can stimulate additional melanin production, darkening existing marks and prolonging their visibility. Consistent use of a broad-spectrum, non-comedogenic sunscreen is therefore an essential part of managing PIH, particularly for individuals using retinoids or exfoliating acids that increase photosensitivity. Gentle cleansing and appropriate moisturization help maintain barrier integrity and reduce the risk of irritation-induced pigment changes.
Improvement in post-inflammatory hyperpigmentation typically occurs gradually over weeks to months, depending on depth and individual skin biology. Superficial discoloration may fade more quickly, while deeper pigmentation can take longer to resolve. Unlike active acne lesions, PIH does not contain pus or swelling and cannot be “extracted.” Aggressive treatments or excessive exfoliation may increase inflammation and delay recovery.
While post-inflammatory hyperpigmentation can be distressing, it is generally temporary. Persistent, widespread, or resistant pigmentation may benefit from evaluation by a qualified healthcare professional, who can assess whether prescription-strength topicals or in-office procedures are appropriate. Addressing both active acne and pigment regulation simultaneously offers the most effective strategy for improving overall skin clarity and tone over time.
