The Pink Elephant Lady
Why Do Some Deodorants Cause Armpits to Darken?
Darkened armpits are often a result of post-inflammatory hyperpigmentation (PIH), a darkening of the skin that occurs after there is damage or irritation to the skin. Common causes include (but are not limited to) acne, eczema, pseudofolliculitis barbae (razor bumps), atopic or allergic contact dermatitis, insect bites, skin exposure to topical irritants, trauma, psoriasis, certain medications, or certain cosmetic procedures. The root cause of PIH is increased melanin production (African Americans are more susceptible to PIH because they have more melanin)*. Melanin is the pigment that defines the color of a person's skin, and an increase in melanin is triggered when skin heals after inflammation or injury. This is EXACTLY what happens during tanning; that's why there's no such thing as a healthy tan! When skin is burned and damaged by the sun's rays, it makes melanin to try to protect skin from further damage, which causes skin to darken.

If the ingredients in your deodorant are causing irritation to armpit skin, this can cause PIH. Common culprits include, but are not limited to, baking soda, parabens (a class of preservatives), fragrance, propylene glycol, and lanolin.
According to the American Academy of Dermatology, even if you have naturally dark skin (dark skin can get darker after prolonged, unprotected exposure to sunlight) or always tan and never burn, this still means the sun is damaging your skin! Furthermore, sun exposure can make hyperpigmentation worse, and can result in uneven patches of color and/or freckling. If you have patches of discoloration/hyperpigmentation, it is especially important to apply sunscreen in those areas before sun exposure.
Shaving the armpits can also contribute to skin darkening. Shaving only cuts the hair off at the surface of your skin, and darkness may be just the hair follicles that are right below the surface of your skin. Shaving too often, shaving dry, or shaving with a dull blade can lead to skin hardening and skin darkening because of the irritation and abrasions caused. Sensitive skin can also react to irritants in shaving creams and lotions such as fragrance.
What does NOT cause armpit discoloration is 'pit detox'. Steer clear of any deodorant manufacturer that tries to convince you that their product caused your armpits to turn dark because you're 'detoxing' from conventional deodorants. There is no such thing as a pit detox . For some reason, this is a tough statement to get people to believe, and I'm not sure why. If you've been using an antiperspirant for a while and you switch to an aluminum-free deodorant, you're going to sweat more - the aluminum salts in antiperspirants temporarily block sweat ducts, and that's why you don't sweat if you use them. If you want to call this a 'detox', so be it. Also, if the grocery store brand of deodorant you've been using was irritating your skin, and you stop using it, any irritation the conventional brand caused will probably go away. Again, maybe people want to call this a 'detox', too. But it's irritation causing darkened armpits, not a 'pit detox'.
What Can You Do About Armpit Darkening?

I've seen many bloggers suggest applying baking soda to lighten armpits. I'd be very, very careful with this. Baking soda in 'natural' deodorants is often the culprit when people get armpit rashes - baking soda is alkaline, and too much of it can disturb skin's pH level. Be careful of manufacturers or bloggers that tell you their product gave you a rash because your body must be too acidic or too alkaline, so you need to change your diet - human blood has a VERY narrow pH between 7.35 and 7.45 - go much outside this range, and you've got alkadosis or acidosis, and need to seek medical attention immediately. The human stomach, on the other hand is very acidic, with a pH of 3.5 or below, so it can break down food. The pH of your pee changes based on what you eat - that's how your body keeps the level in your blood steady. But NOTHING you eat will significantly change your blood's pH level. The 'alkaline diet' of eating lots leafy greens and veggies versus a diet of mostly alcohol, refined carbs and processed food is a good idea, but not for the reason the alkaline diet book authors think it is: it's just healthier all the way around, not because it makes your body 'alkaline'.
How Do I Fix Darkened Armpits?
Sounds simplistic, but to figure out if your deodorant is causing the darkening of your armpits, stop using it for a few weeks and see what happens. You may want to stop shaving for a while, too, and see if that helps. Other treatments for darkened armpits include prescription and over the counter topical treatments like hydroquinone, retinoids, or corticosteroids. Natural products that lighten or 'peel' skin include ingredients like azelaic acid, glycolic acid, and kojic acid. Procedures include microdermabrasion and light chemical peels.
I've seen potato slices, cucumber slices, lemon juice, apple cider vinegar, turmeric, aloe vera, and coconut oil suggested as home-based, DIY remedies. If your skin is irritated or open in any part of your armpit, don't try any of these until skin has healed. I haven't tried any of them.
A salicylic acid-containing skin scrub might be helpful if the build up of dead skin cells is causing armpit darkening, but DO NOT use a scrub if your armpit is irritated in any way.
This blog post was about armpit darkening due to deodorant - there are other causes of armpit darkening. Most are harmless and temporary, but some are more serious. I'm not going to get too heavy into these, because I don't want to be like WebMD and Google University and get everyone convinced they have cancer. Acanthosis nigricans (AN) is a skin disorder characterized by darkening and thickening of the skin, occurring mainly in the folds of the skin in the armpit, groin, and back of the neck. AN is most commonly benign, but can be malignant. Benign AN is often found in conditions that are associated with an elevated insulin blood level, such as in diabetes and obesity. In rare cases, AN can be casued by stomach cancer, adrenal gland disorders, disorders of the pituitary gland, low levels of thyroid hormones or high doses of niacin.
DISCLAIMER:
These statements and the products of this company are not intended to diagnose, treat, cure or prevent any disease. This website is for educational purposes only and is not meant to replace the advice of your physician or healthcare provider.
*If you'd like more information about skin conditions that affect people of color, check out the educational resources on the Skin of Color Society's website (http://skinofcolorsociety.org/dermatology-resources/). I'm proud to be a non-physician associate member! Skin of Color Society is a professional organization dedicated to promoting awareness of and excellence within the area of special interest of dermatology, skin of color. Individuals with skin of color include but are not limited to African Americans, Asians, Hispanics or Latinos, Native Indians and Pacific Islanders. The Skin of Color Society is committed to a wide range of educational and investigational pursuits designed to impact individuals with skin of color and to ensure the success of dermatologists in serving these individuals.