How to care for dark underarms

Why are your underarms darker?

Dark underarms can come from genetics, shaving irritation, tight clothing, excessive sweating or reactions to products. Post inflammatory hyperpigmentation means extra pigment left after inflammation or injury. In medium to dark skin tones, irritation can trigger extra melanin, the substance that gives skin its color. Repeatedly irritating the area can keep creating new marks while older ones fade.13

Darkness with a change in texture needs a different approach. Acanthosis nigricans is a condition that causes darker, thicker, velvety patches, commonly in the underarms, neck and groin. The patches can feel dry, sometimes itch and have small skin tags. They often appear gradually without other symptoms. Those features are a reason to book an appointment, not a way to diagnose yourself.2

What should you do first?

1. 1Check for new patches or a change in texture. Arrange a medical assessment if the darkness is new, thick or velvety, or if you are unsure what caused it.
2. 2Reduce the number of products you apply. If deodorant seems to cause a rash or irritation, change it rather than adding another product over the reaction.
3. 3Choose products labelled for sensitive skin and without fragrance. Consider dyes and preservatives as possible triggers too.
4. 4Address repeated irritation. Shaving and rubbing from tight clothing can contribute to dark underarms, so reduce those triggers rather than trying to exfoliate the marks away.
5. 5Once the cause is addressed, discuss a pigment treatment if you still want to lighten the area. Treat an active skin condition before concentrating on the color it leaves behind.

The word "natural" is not a reason to choose a deodorant, even if the packaging has recruited a leaf. Natural products can still contain fragrances, dyes and preservatives that irritate skin. Choose by the formula and how your skin tolerates it, not by that word on the front.1

Can you still use antiperspirant?

Deodorant reduces odor; antiperspirant reduces sweat by temporarily blocking sweat glands. If an antiperspirant is part of treatment for excessive sweating, apply it to dry skin before bed and let it dry completely. Dry skin lowers the chance of irritation. Treatment usually brings sweating under control within a few weeks, after which application is often reduced to once or twice a week as needed.5

Tell your dermatologist if antiperspirant causes irritation or underarm discoloration. Adjustments can include a different formulation, longer gaps between applications or making sure the skin is very dry. If heavy sweating interferes with daily life, seek treatment rather than repeatedly applying an irritating product. Moisture and friction in skin folds can also contribute to intertrigo, an inflamed rash, sometimes with an infection.56

Which treatments can lighten dark underarms?

Treatment depends on whether the problem is leftover pigment, thickened skin or an underlying health condition. Keep the focus on the cause rather than collecting brightening products, because an underarm routine does not need a purchasing department. For suspected acanthosis nigricans, consult a clinician before using dark spot products: they can irritate the skin and worsen the problem.7

• For persistent underarm pigment, a doctor can consider creams containing niacinamide, retinol, kojic acid or hydroquinone.
• For abnormally thick skin, creams containing urea or ammonium lactate can help dissolve the thickened outer layer.
• For acanthosis nigricans, a clinician can consider treatments containing ammonium lactate, tretinoin or hydroquinone to improve appearance, while addressing the underlying cause.
• Office treatments can include chemical peels or dermabrasion. Laser treatment is another possible option, but it is not a common treatment for dark underarms.

Acanthosis nigricans does not always need cosmetic treatment. If no underlying condition is found, you can decide whether to treat its appearance. When diabetes, insulin resistance or a hormonal condition is responsible, managing that condition takes priority over lightening the patches. Skin can improve with treatment, although the dark areas do not always disappear completely.47

What should you avoid?

Do not scrub thick, velvety patches in an attempt to wash them off: washing does not remove acanthosis nigricans. Repeated exfoliation can irritate underarms. Stop a cosmetic product if it burns or stings. Never apply liquid bleach to skin. Some imported lightening products have contained unlisted mercury or steroids, so choose a product recommended by your dermatologist rather than an unknown lightening cream.137

How long does fading take?

For general hyperpigmentation, a mark a few shades darker than your natural skin color usually fades within 6 to 12 months after the cause stops. Deeper pigment can take years. These are general pigment timelines, not a timetable for every dark underarm. Acanthosis nigricans patches should fade over time when the cause is treated; the priority is treating that cause, not increasing exfoliation while you wait.23

If clothing leaves your underarms exposed outdoors, apply sunscreen before going outside. For hyperpigmentation, choose tinted sunscreen with iron oxide, SPF 30 or higher, broad spectrum protection and water resistance. Reapply every two hours outdoors and after swimming or sweating.3

When should you see a doctor?

Book an appointment for new dark patches or skin changes you cannot explain. Seek prompt assessment if thick, dark patches appear suddenly or spread rapidly. Rarely, rapidly developing, widespread acanthosis nigricans can be associated with cancer. Persistent itching or inflammation after changing an irritating deodorant also needs assessment.124

A doctor can usually recognize acanthosis nigricans by examining the skin. If the cause is unclear, blood tests can check for diabetes; a skin biopsy is rarely needed. Mention weight changes, a family history of diabetes, irregular menstrual cycles and unusual hair growth. Dark patches alone do not mean you have diabetes: acanthosis nigricans also occurs in otherwise healthy people.147

Bring a list of your medicines, including hormone treatments, contraceptive pills and steroids, because some can contribute to acanthosis nigricans. Do not stop a prescribed medicine yourself. Ask the prescriber whether discoloration could be a side effect and whether a change is appropriate.23