Common causes of particularly smelly toenail crevices include hygiene factors, onychomycosis, and fungal infections. 1. Hygiene factors: toenails are not trimmed regularly, and it may be difficult to clean the gaps between toenails when washing feet. Over time a large amount of dead skin, fungus or dust will accumulate in the crevices of the toenails, producing a foul odor. 2. Inguinitis: Inguinitis is usually caused by a bacterial infection, which can lead to localized pus and infection around the nail. When toenails are too long, they cannot be cleaned adequately and the buildup of bacteria can give off an unpleasant odor. 3. Fungal infections: Fungi can easily form in uncleaned nail crevices. Fungi can decompose the nail cuticle to form a yellowish sludge-like substance in the process of reproduction, which is accompanied by a distinctive bad odor. When the patient’s toenails are particularly smelly, he should do a good job of cleaning his feet and maintain good hygiene habits, which can avoid the situation. For the emergence of nail groin infection, fungal infection, should be timely treatment.