Painful penicillin injections are generally normal and may be caused by factors such as potassium ion stimulation, thicker injection needles, and cold stimulation. In general, if no abnormal symptoms appear, patients need not worry too much, but measures can be taken to effectively relieve the pain. Common causes 1, potassium ion stimulation: penicillin contains potassium ion, which is usually more irritating to human peripheral blood vessels and can cause pain after injection; 2, thicker injection needles: penicillin in lysozyme particles molecules are large and difficult to dissolve in water. When intramuscular injection, in order to prevent needle blockage, a large syringe is usually used, which may cause pain at the puncture site; 3, cold stimulation: penicillin can cause water solubility to become poor due to low temperature, which can trigger cold stimulation, leading to muscle contraction at the injection site, increasing the difficulty of injection, i.e., the chance of needle blockage, and intensify the pain; 4, other factors: such as the injection site due to impaired subcutaneous circulation, there is reflux obstruction, which may lead to local hard knots and thus produce painful injection. Injections may also cause increased pain if the drug is pushed at a faster rate. To relieve pain, keep the area clean and dry, avoid sitting for a long time, and put a soft cushion when sitting to relieve discomfort. For some penicillin injections, lidocaine lysozyme can also be used under medical advice to relieve pain. Precautions If the painful area appears red, swollen and other abnormalities, you need to consult your doctor promptly whether adverse reactions occur to avoid serious consequences.