From the Guidelines
Prophylactic antihistamines do not prevent anaphylaxis.
Key Points
- The use of antihistamines, such as H1 or H2 antihistamines, has been evaluated for the prevention of biphasic anaphylaxis, but the evidence suggests that they do not provide significant benefit 1.
- The certainty of evidence is very low, and the number needed to treat (NNT) to prevent one episode of biphasic anaphylaxis is high, ranging from 20 to 72 for H1 antihistamines 1.
- Antihistamines may be used as secondary therapy to treat symptoms such as urticaria and itching during anaphylaxis, but they should not delay the administration of first-line treatment with epinephrine 1.
- The potential harms of antihistamines, such as altered level of consciousness with first-generation antihistamines, and the uncertainty of their benefit, make them an unreliable method for preventing anaphylaxis 1.
Treatment Considerations
- Epinephrine auto-injectors remain the first-line treatment for anaphylaxis, and antihistamines should not be used as a substitute 1.
- In high-risk individuals, other prophylactic treatments, such as omalizumab or corticosteroids, may be considered, but antihistamines are not a recommended option 1.
From the Research
Prophylactic Antihistamines and Anaphylaxis Prevention
- There are no research papers provided that directly investigate the effectiveness of prophylactic antihistamines in preventing anaphylaxis 2, 3, 4, 5, 6.
- The studies provided focus on various topics, including the efficacy and safety of agomelatine in treating generalized anxiety disorder 2, 3, 5, the efficacy and safety of oral semaglutide in adults with type 2 diabetes 4, and the efficacy and safety of dapagliflozin as add-on therapy in patients with type 2 diabetes 6.
- None of these studies address the use of prophylactic antihistamines for anaphylaxis prevention, and therefore, no conclusions can be drawn from the provided evidence.