Antihistamines

What are antihistamines?

Antihistamines are medications formulated to counter the effects of histamines in the body. They are typically utilized to manage allergic reactions, such as seasonal allergies. In dermatology, antihistamines find their primary use in addressing issues like chronic itching and urticaria (hives).

How do antihistamines work?

Antihistamines work by blocking the histamine receptors in the body, preventing the histamine from exerting its effects, which are primarily responsible for symptoms like itching and hives. By doing so, these medications can help alleviate discomfort and other symptoms associated with allergic reactions and certain skin conditions.

What are possible side effects of antihistamines?

Antihistamines' side effects can vary depending on the specific drug in use. Here are the potential side effects of various antihistamines:

  • First-Generation Antihistamines (e.g., diphenhydramine or hydroxyzine):

    • Drowsiness

    • Dry mouth or mucous membranes

    • Elevated Heart rate

    • Urinary Retention or Constipation

    • "Hangover" symptoms on the following day

  • Second-Generation Antihistamines (e.g., loratadine, cetirizine, or fexofenadine):

    • Drowsiness (mainly associated with cetirizine, occurring in about 10% of users)

  • H2 Blockers (e.g., famotidine or ranitidine):

    • Less likely to cause drowsiness compared to first-generation antihistamines

Note: If considering switching to newer generation antihistamines due to side effects, loratadine and fexofenadine are generally recommended as first options due to their minimal drowsiness effects.

How are antihistamines used?

In dermatology, antihistamines are frequently prescribed at doses higher than the usual over-the-counter recommendations to effectively manage conditions like chronic urticaria. For instance, the dosage for loratadine, typically used for seasonal allergies, might be increased to up to four pills daily for hives management. These escalated doses are endorsed by professional organizations like the American Academy of Dermatology for their safety and effectiveness.

Precautions:

  • It is vital to adhere to the prescribed dosage, even if it exceeds the suggestion on over-the-counter packaging, to ensure the medication's efficacy.

  • Always consult with a healthcare provider for personalized medical advice.

THIS CONTENT IS INTENDED SOLELY FOR EDUCATIONAL PURPOSES AND MAY NOT BE COMPREHENSIVE. IT DOES NOT CONSTITUTE MEDICAL ADVICE. PLEASE REFER TO OUR TERMS OF USE FOR FURTHER DETAILS. ALWAYS CONSULT WITH YOUR HEALTHCARE PROVIDER BEFORE MAKING ANY MEDICAL DECISIONS.