Long-term use of anti-allergy drugs, more or less will have certain side effects, the number of side effects, but also depends on the use of the first generation or the second or third generation.

First-generation antihistamines (such as paracetamol, phenylephrine), there are obvious sedative effects and central nervous system adverse reactions, the most common are drowsiness and fatigue, prolonged reaction time, etc. In addition, it can cause dry mouth, dry eyes, blurred vision, constipation, urinary retention, etc., and can also induce glaucoma.

The second generation of antihistamines, side effects are rare, almost no obvious anticholinergic effect and sedative effect, commonly used drugs are cetirizine, loratadine, imipramine, ibastine and so on.

Third-generation antihistamines, such as desloratadine, fexofenadine, and levocetirizine, have milder side effects.

Topical antihistamines such as nasal sprays, eye drops, and skin creams. Not only can avoid the adverse effects of oral administration of the first and second generation of antihistamines, but also to achieve the same efficacy as oral medication. Moreover, it has a fast onset of action, has no obvious central nervous system side effects and cardiotoxicity, and does not produce drug resistance in long-term application.

In summary, it is recommended that you use it externally.