Many individuals are unaware of their own body odor or bad breath due to a phenomenon called olfactory fatigue, where the brain habituates to persistent smells. This occurs because the olfactory system, specifically the olfactory bulbs in the nose, down-regulates signals to the brain when exposed to the same scent repeatedly, allowing for heightened sensitivity to new or potentially dangerous odors, such as smoke.
This desensitization is a protective mechanism, according to Professor Carl Philpott of Norwich Medical School and Simon Gane, a consultant rhinologist. While the nose becomes less reactive to a specific familiar smell, the overall sense of smell does not diminish. Research from the Technical University of Dresden demonstrated that sensitivity to a specific scent can be regained after a period without exposure.
Beyond olfactory fatigue, other medical conditions can affect a person's sense of smell or contribute to body odor. Approximately 3.3 million people experience anosmia, a complete loss of smell, often linked to nasal polyps, hay fever, nose trauma, or brain tumors. Infections, including COVID-19, can also temporarily or permanently impair smell.
Excessive sweating is a common cause of body odor, as bacteria on the skin break down sweat, producing odor compounds. Hormonal fluctuations, such as those during menopause, or conditions like hyperhidrosis can increase sweating. Certain medications, including some antidepressants and antibiotics, may also contribute by increasing perspiration.
Diet can play a role, with sulfur-rich foods like garlic and onions potentially exacerbating body odor. The materials of clothing, such as polyester and nylon, can trap moisture and heat, creating an environment conducive to bacterial growth.
Bad breath, or halitosis, affects about 25% of the UK population and can also be a result of olfactory fatigue. The tongue, particularly the back of it, can harbor bacteria and food particles, leading to unpleasant odors. Gum disease and reduced saliva production, sometimes due to medications, can also contribute.
Detecting unnoticed body odor or bad breath can be challenging. For bad breath, a simple test involves licking the inside of the wrist, letting it dry, and smelling it. Observing the tongue for a white or yellow coating can also be an indicator of bacterial buildup. Maintaining good oral hygiene, including regular brushing, flossing, tongue cleaning, staying hydrated, and dental check-ups, is crucial for preventing halitosis.
A 'shirt test' is suggested for body odor: wearing a shirt, removing it, leaving it in another room for about 20 minutes, and then smelling the underarms. This allows the nose a fresh assessment of familiar body scents. While these methods can offer clues, consulting a trusted friend or healthcare professional may be necessary for a definitive assessment.