Underarm discoloration
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Underarm hyperpigmentation is a darker discoloration of the skin in the underarm area resulting from increased melanin production, its uneven distribution, or thickening of the epidermis. Most often, it is benign and results from chronic friction, irritation after hair removal, reactions to cosmetics, or past skin inflammation. However, dark, thickened, and velvety skin may correspond to acanthosis nigricans, which can be a cutaneous marker of insulin resistance. Because lesions with different causes can have a similar appearance, effective lightening should be preceded by a skin assessment. The foundation of management is reducing the irritating factor and treating the condition responsible for the discoloration, followed by the application of appropriately selected depigmenting preparations or procedures.
Underarm discoloration - why does it occur
Skin color depends primarily on the amount, type, and distribution of melanin. This pigment is produced in melanocytes and then transferred to keratinocytes, which are the basic cells of the epidermis. Inflammation can stimulate melanocytes, among others, through prostaglandins, leukotrienes, and cytokines. This leads to post-inflammatory hyperpigmentation, particularly visible in individuals with higher skin phototypes.
The most common causes of underarm darkening include:
- mechanical friction, associated with tight clothing, excess body weight, or the anatomy of skin folds;
- shaving, hair plucking, and other micro-injuries to hair follicles;
- folliculitis, ingrown hairs, and recurrent pustules;
- contact dermatitis from deodorants, fragrances, preservatives, or depilatory products;
- chronic chafing (intertrigo), excessive sweating, and epidermal barrier dysfunction;
- acanthosis nigricans, most commonly associated with hyperinsulinemia and obesity;
- certain medications, endocrine disorders, and, much less frequently, systemic diseases.
Differential diagnosis should also take into account skin fold infections, erythrasma, candidiasis, inverse psoriasis, and hidradenitis suppurativa (acne inversa). Itching, burning, foul odor, flaking/scaling, nodules, abscesses, or scars are not features of simple discoloration and require medical evaluation.
The appearance of the lesion is also important. A flat, brown patch following irritation suggests post-inflammatory hyperpigmentation. Symmetrical, gray-brown, thickened, and velvety skin suggests acanthosis nigricans. Sudden, rapidly progressing, and extensive changes, especially in a lean adult, should be urgently evaluated by a doctor.
Underarm discoloration - what role does hair removal play in it
Hair removal can initiate or perpetuate hyperpigmentation if it causes epidermal damage or folliculitis. Passing a razor over the skin multiple times, shaving without a lubricant, using a dull blade, and shaving against the direction of hair growth promote microtrauma. The healing of inflammation can leave behind brown post-inflammatory spots.
Wax, sugar paste, and mechanical epilators pull hair out along with the bulbs. In some people, they cause transient erythema, folliculitis, or ingrown hairs. Chemical depilatory products, on the other hand, can cause contact dermatitis, especially when left on the skin for too long or applied to damaged epidermis.
In the prevention of shaving irritation, it is recommended to:
- use a clean, sharp blade and a friction-reducing product;
- shave in the direction of hair growth, without repeatedly going over the same area;
- avoid deodorants containing alcohol or fragrances immediately after hair removal;
- use a gentle moisturizing and epidermal barrier-restoring product;
- discontinue hair removal until active inflammation has healed.
Laser underarm hair removal, available at Ambasada Urody, can, upon completion of a series, reduce the amount of hair, ingrown hairs, and the frequency of shaving, thereby decreasing subsequent microtrauma. However, it is not a direct whitening treatment. Incorrectly selected parameters, a suntan, or a procedure performed on irritated skin can cause burns and exacerbate post-inflammatory hyperpigmentation. Therefore, parameters must be adjusted to the phototype, hair color, and current skin condition.
Underarm discoloration - when it can indicate insulin resistance
A connection with insulin resistance should primarily be suspected when the lesion corresponds to the clinical presentation of acanthosis nigricans. These are usually symmetrical, poorly demarcated, brownish or grayish-brown patches with a velvety, thickened surface. They may involve the armpits, the nape of the neck, the groin, the areas under the breasts, and other skin folds.
In hyperinsulinemia, high insulin levels can activate insulin-like growth factor IGF-1 receptors in keratinocytes and fibroblasts. This stimulates cell proliferation, leading to papillomatous thickening of the skin. Thus, the dark appearance of the lesion results not only from an increased amount of melanin, but also from hyperkeratosis, which is the excessive keratinization of the epidermis.
The likelihood of metabolic disorders is increased by:
- overweight or obesity, especially abdominal;
- a history of type 2 diabetes or gestational diabetes;
- a family history of diabetes;
- arterial hypertension or an abnormal lipid profile;
- irregular periods, hirsutism, and other features of polycystic ovary syndrome;
- the presence of similar lesions on the nape of the neck and in the groin.
Discoloration alone does not allow for a diagnosis of insulin resistance. The doctor assesses the overall clinical picture and may order, among other things, fasting glucose, glycated hemoglobin, and a lipid panel. An oral glucose tolerance test is performed for specific indications. Insulin levels and the HOMA-IR index should not be interpreted independently, as there is no single universal diagnostic threshold appropriate for all laboratories and populations.
In acanthosis nigricans, the most important aspect is treating the metabolic cause. Reducing excess body weight, regular exercise, and doctor-guided management can gradually improve the appearance of the skin, whereas skin lightening alone does not resolve the systemic disorder.
Underarm discoloration - how to lighten it
Treatment should depend on the diagnosis. First, irritation, folliculitis, eczema, or metabolic disorders must be controlled. An attempt at intensive exfoliation of actively inflamed skin may worsen discoloration.
Topical treatment uses substances that affect various stages of melanogenesis and epidermal renewal:
- azelaic acid reduces tyrosinase activity and has anti-inflammatory properties;
- niacinamide reduces the transfer of melanosomes to keratinocytes and supports the skin barrier;
- retinoids normalize keratinization and accelerate epidermal renewal, but may initially cause irritation;
- glycolic, lactic, and salicylic acids have an exfoliating effect, and urea softens the thickened stratum corneum;
- hydroquinone and other potent depigmenting drugs should only be used under medical supervision.
Topical glucocorticosteroids, such as desonide studied in underarm hyperpigmentation, are not brightening cosmetics. Their uncontrolled use in skin folds carries the risk of skin thinning, stretch marks, and infections.
Treatments available at Ambasada Urody that, following qualification, may be considered in the therapy of pigmentation lesions include:
- chemical and acid peels, including preparations with mandelic, azelaic, glycolic, salicylic, or pyruvic acid;
- medical peels, such as TCA, VI Peel, PRX-T33, and Ferulac Valencia Peel;
- depigmentation therapies Cosmelan and Dermamelan;
- needle or microneedle mesotherapy with appropriately selected depigmenting ingredients, such as tranexamic acid;
- pigmentation technologies Alma DyeVL PRO and ICON Palomar MaxG, utilizing pulsed light;
- selected laser treatments, including fractional technologies, if appropriate indications exist;
- laser hair removal of the underarms, when recurring post-shaving inflammation or ingrown hairs are significant factors.
Not every treatment intended for treating facial discoloration is automatically suitable for the skin of the underarms. The underarm fold is moist and prone to friction and occlusion; therefore, the possibility of using a specific preparation or device in this area requires individual confirmation during a consultation. Laser and IPL procedures can lighten lesions, but they also carry the risk of a paradoxical increase in hyperpigmentation, especially in darker skin phototypes or with overly aggressive settings.
Underarm discoloration - how to prevent its return
The durability of improvement depends primarily on eliminating the triggering factor. Even an effective treatment will not prevent a recurrence if the skin remains chronically irritated or if acanthosis nigricans accompanies untreated metabolic disorders.
Prevention includes:
- reducing friction and choosing breathable, not overly tight clothing;
- gentle hygiene without scrubbing the skin and without coarse-grained scrubs;
- regular moisturizing with a fragrance-free product;
- cautious introduction of new deodorants and cosmetics;
- proper shaving technique or considering laser hair removal;
- treatment of folliculitis, eczema, and hyperhidrosis;
- avoiding hair removal on irritated skin;
- following post-treatment recommendations and maintaining appropriate intervals between procedures;
- body weight normalization and glycemic control if acanthosis nigricans of metabolic origin has been diagnosed.
Home remedies based on lemon juice, baking soda, undiluted acids, and intense abrasion should be avoided. They can damage the epidermal barrier, trigger contact dermatitis, and leave even darker hyperpigmentation. The effects of therapy should be evaluated after several to a dozen weeks, as the removal of melanin from the epidermis is a gradual process. If the lesion progresses rapidly, becomes thickened, spreads to other areas of the body, or is accompanied by metabolic symptoms, the appropriate course of action is a dermatological and internal medicine consultation, rather than another brightening treatment.
