Hair two days without washing there is a foul odor to consider is a bad habit, ringworm, seborrheic dermatitis and so on. 1. bad habits: if usually often stay up late, or usually work life in the pressure is relatively large, often eat spicy stimulating greasy food, will lead to sebaceous gland secretion exuberant, grease secretion will be gathered on the surface of the hair and bacterial chemical reaction, coupled with the cleaning is not in place, the accumulation of sebaceous dirt, odor. 2. Tinea capitis: Tinea capitis is a fungal infection of the hair area, which will appear as yellow scabs, pimples and other symptoms, and the overpopulation of fungi will also cause odor, usually accompanied by itching, hair loss and other symptoms. 3. seborrheic dermatitis: seborrheic dermatitis is a chronic inflammation that occurs in the seborrheic overflow area, seborrheic dermatitis if it occurs in the head there will be erythema adhering to the oily flakes, the serious ones will have greasy yellow or brown scabs, and in addition emit the odor of sebum decomposition. Hair two days without washing the odor, there may be other reasons, such as scalp psoriasis, other fungal infections (scalp yeast infection), it is recommended to go to the hospital for a detailed examination, by the doctor to clarify the cause of the standardized treatment.