When a small injection (intramuscular injection) hurts in the buttocks, it is usually normal. If the pain is more intense, it may be due to soft tissue damage, obvious drug irritation, low liquid temperature and other factors. 1. Soft tissue damage: patients in daily life, small injection, the needle eye and the needle channel will cause some damage to the surrounding soft tissues, in the injection process, will damage the local skin and other soft tissues, resulting in the phenomenon of pain. 2. Obvious drug irritation: some drugs are obviously irritating, such as penicillin powder injection, when the drug concentration is too high during the injection process, it will lead to the rapid formation of hypertonicity, which will stimulate the nerves and may cause severe pain. 3. Low temperature of the liquid: the temperature of the liquid is too low when the patient is taking small injections, which may stimulate the surrounding blood vessels, causing vasoconstriction, which leads to the phenomenon of pain. Intramuscular injection of buttocks pain, may also be due to improper injection needle method, generally do not worry too much when the pain is mild. If the pain is more intense, it is recommended to analyze the cause and consider solutions.