Experts are warning people to rethink how they use antihistamines to ease their allergies.
Millions of people are plagued by blocked noses, hives and itchy, watery eyes during the pollen season and rush to their local pharmacy for over-the-counter relief.
However, Derek Chu, a McMaster University allergy expert and clinical scholar, claims allergy aids are commonly used incorrectly and has offered some advice for sufferers this year.
"People need to rethink what they stock in their home cabinets as allergy medicines, what hospitals keep on formulary, and what policymakers recommend," Chu said. "The message needs to get out. This publication is on time for the spring allergy season and as Covid-19 vaccines roll out, for which rashes are common and antihistamines can be helpful."
Experts say many people are not using the newer, more effective forms of antihistamines.
"There are new modern second-generation antihistamines that are potent, specific, fast-acting and of proven safety which everyone should be using to treat allergic rhinitis and hives," explained co-author Gordon Sussman, professor of medicine at University of Toronto's Temerty Faculty of Medicine.
The study, which was published in the Canadian Medical Association Journal (CMAJ), listed five facts all allergy sufferers should know.
1. Antihistamines are among the most commonly and incorrectly used medicines worldwide.
Antihistamines can relieve symptoms of hay fever and hives, but not for the management of asthma, eczema, coughs or insomnia.
2. First-generation antihistamines are associated with substantial and sometimes fatal side effects.
Antihistamines with diphenhydramine (Benadryl), chlorpheniramine or hydroxyzine are first-generation antihistamines that can cause drowsiness, impairment of sleep, injury and affect cognitive functions. Overdose can result in death.
3. Newer antihistamines are safer, as affordable and as effective as first-generation antihistamines.
Controlled trials have shown they last longer and carry fewer side effects, such as drowsiness, and chlorpheniramine was replaced by loratadine on the World Health Organization's essential medicines list in 2013 for these reasons.
4. Antihistamines should not be used instead of epinephrine to treat anaphylaxis.
Oral drugs can be used with epinephrine injections to treat anaphylactic reactions, but not as a replacement.
5. Most antihistamines are safe to use during pregnancy and breastfeeding.
Studies have shown that standard doses of antihistamines do not harm foetuses during pregnancy and can be used by breastfeeding mothers. They are also safe for children to use.