People who are allergic to penicillin may have allergic reactions once they take penicillin and other drugs, generally there are mild and severe allergic reactions, as follows: 1, mild: some patients will have a general rash, hives, etc., and may even have dizziness, chest tightness, shortness of breath, nausea, vomiting, abdominal pain, etc. 2, severe: serious patients will have anaphylactic shock, manifested as general wet and cold, blood pressure The patient may even experience respiratory and cardiac arrest. Therefore, people who are allergic to penicillin must not take drugs containing penicillin or semi-synthetic penicillin. In addition, some cephalosporins should be taken with caution to prevent allergic reactions, and once an allergic reaction occurs, it is important to consult a regular hospital promptly.