What are the side effects of benzocaine?
Nov 25, 2025
Source: Cainiu Health
Dr. Wang Lei
Introduction
In general, benzocaine is a local anesthetic that may cause various side effects after use, including local irritation, allergic reactions, methemoglobinemia, worsening of mucosal damage, and contact dermatitis. Benzocaine is commonly used for topical anesthesia on the skin and mucous membranes, and should be used strictly according to the instructions or medical advice.
Under normal circumstances, benzocaine is a local anesthetic that may cause various side effects after use, including local irritation reactions, allergic reactions, methemoglobinemia, worsening of mucosal damage, and contact dermatitis. A detailed analysis is as follows:
1. Local irritation reaction: This is a relatively common side effect. The application site may experience transient redness, swelling, burning sensation, stinging pain, or itching. Symptoms are usually mild and short-lived, caused by the drug's irritation to local skin or mucous membranes, and typically resolve spontaneously after the drug is metabolized without requiring special treatment.
2. Allergic reaction: Some individuals are allergic to benzocaine. Mild cases may present with rashes or urticaria accompanied by significant itching; severe reactions may include angioedema, manifesting as swelling of the eyelids and lips, and in extreme cases, anaphylactic shock with life-threatening symptoms such as difficulty breathing and hypotension.
3. Methemoglobinemia: This is a relatively rare but dangerous side effect of benzocaine. The drug may inhibit reductase activity in red blood cells, leading to elevated levels of methemoglobin and impaired oxygen transport. Patients may develop cyanosis of the lips and nail beds, accompanied by dizziness, fatigue, and shortness of breath.
4. Worsening of mucosal injury: If applied to damaged mucosa, the drug may irritate the injured tissue, increasing pain and exudation, and potentially delaying wound healing. Therefore, application should avoid areas with mucosal damage to reduce the risk of local injury.
5. Contact dermatitis: Long-term or repeated use of benzocaine preparations may lead to contact dermatitis, characterized by well-demarcated erythema and papules at the application site. In severe cases, blisters and scaling may develop, accompanied by persistent itching. Symptoms usually require antiallergic medications for relief after discontinuation of the drug.
Benzocaine is primarily used for topical anesthesia on skin and mucous membranes. It should be used strictly according to instructions or medical advice to avoid overdose or prolonged use. Prior to use, individuals should confirm whether they have any allergies. Use in infants and young children should be cautious to minimize the risk of adverse effects.
