Surely you have ever raised your arms and wondered what this smell is?

If your deodorant is no longer effective, you may need to re-evaluate your deodorant routine. Several external and internal factors can affect your deodorant's effectiveness. These include humidity, altitude, and the microbiome of your skin. Also, certain foods, can affect the performance of deodorant. If you're using a deodorant for several years, you might need to re-evaluate its effectiveness based on these changes.

"Perceived differences in smell may have to do with how much the person is actually sweating," says board-certified dermatologist and founder of LM Medical Morgan Rabach, MD. Things like stress, hormonal changes, new medications, and different lifestyle factors can all impact how you sweat, and your go-to deodorant may not be able to stand up to the new situation. "There also can be changes in the natural bacterial flora that live on the skin, [as in] increased amounts, that lead to more bacteria interacting with the sweat and making the odor," she adds.

Stress

Your deodorant may be stopping working because of stress. There are several reasons for this. 

When people are under high levels of stress, the glands in the armpits may produce more sweat, sometimes with a strong sulfurous odor. This stress sweat is thicker and contains more proteins, fatty acids, and steroids than normal sweat. As a result, it tends to be odorous. This is because it takes a longer time to evaporate off the skin, which gives bacteria enough time to mix with the sweat and create body odor.

When you're stressed, the sympathetic nervous system is activated and this can cause you to perspire excessively. Fortunately, the most effective remedy for a sweating problem caused by stress is to use clinical strength antiperspirant. 

Hormones

Sometimes, your body is experiencing a change in hormones, which can affect the way it produces sweat. A change in your hormonal levels can cause your deodorant to stop working.

The most common hormonal change associated with bad body odor is menopause. A common side effect of menopause is hot flashes, which can lead to increased perspiration. The more sweat, the more foul-smelling compounds are produced as a result of the breakdown of extra sweat by bacteria.

Eating Habits

What we eat can play a significant role not only in body odor, but also in foot odor and bad breath. The nutrients and compounds that foods contain are essential for daily sustenance. However, some of them, especially when consumed in excess, can influence the smell. 

Foods commonly associated with foul-smelling problems include red meat, seafood, egg yolk, garlic, onions, yogurt, beans, asparagus, broccoli, cabbage or cabbage, and spices such as mustard.

Medication

Sometimes underlying medical condition can affect the way your body secretes sweat.

Also, a common side effect of many drugs is perspiration. Antipsychotic and antidepressant medications are known to produce it, as well as other medicines. In addition, overuse of aspirin and acetaminophen can also lead to increased sweat production.

Poor Hygiene

Another reason why deodorant may stop working is because of poor hygiene. Poor hygiene can lead to the accumulation of bacteria that cause bad odor. Many times we try to hide that bad smell using deodorants or perfumes, but more than fighting the problem we make it worse. 

Sometimes there's been too much product buildup under your armpit, which can lead to a lack of effectiveness. In order to fix the situation, take a break from using product on your armpits for three or four days to allow them to return to their natural state, then test your go-to product again. If it still doesn't work, it may be time to try a new brand.