What causes armpits to have a sour smell?

Sour or foul-smelling underarms are common in people with hyperhidrosis. Underarm odor occurs when bacteria on the surface of the armpits come into contact with sweat. Underarm odor can be reduced with the use of deodorants, anti-odors and good body hygiene.

Underarm odor is a problem that many people are facing. This condition is also known as bromhidrosis (body odor). In addition to causing feelings of inferiority when in contact with people around, smelly armpits are usually not cause for concern.
MORE: Why do armpits stink?

Sour underarms are caused by sweat in contact with bacteria on the skin. This condition often occurs in people with hyperhidrosis, mainly in the areas of the hands, feet, and armpits. There are two main types of sweat glands, eccrine and apocrine. While the eccrine glands are spread all over the surface of the body, the apocrine glands are only active in areas with a lot of hair follicles, like the groin and armpits. Both of these glands only start to work when you hit puberty, which is when you start to notice body odor.

Treatments for underarm odor depend on the severity and underlying cause of the body odor, such as poor hygiene, not using the right products, or a sign of an underlying medical condition .
Using an over-the-counter (OTC) deodorant or antiperspirant daily after bathing can reduce underarm odor. You may need to try a variety of products before you find the right one for you.
Antiperspirants help improve underarm odor by temporarily blocking sweat-draining pores. The less sweat is produced on the surface of the skin, the less smelly armpits will be. Deodorants prevent sour underarms with compounds that suppress odors but don't stop perspiration. Both of these products often contain alcohol, which makes the skin acidic, which inhibits the formation of bacteria that are responsible for the odor of sweat.
If deodorants and antiperspirants don't work, see your doctor for advice on using prescription deodorants. For example, Botox is a substance that is well known for its ability to smooth wrinkles on the face. In addition, it has another application that is injected into the sweat glands to reduce both the smell of sweat and the amount of sweat produced. This is a common treatment for people with hyperhidrosis.
However, Botox is not a long-term solution as the injections only last a few months. You will need to re-inject Botox when you need to prevent sweating when the drug wears off.

Prevent underarm odor in the first place with these simple measures:
Shower daily with soap, as well as shower after strenuous activity such as exercise or sports to remove bacteria and sweat cause odor. Wear loose, breathable fabrics like cotton, linen, and moisture-wicking blends to help keep you drier. Shaving or waxing the underarm area regularly helps to clean the bacteria on this skin area, thereby significantly reducing the smell of sour armpits. Managing stress and reducing anxiety can help minimize the physiological sweat response. If multiple deodorants or antiperspirants have been used without success, see your doctor to rule out underlying medical conditions and recommend stronger treatments.

Reference source: healthline.com