Onions and garlic are members of the allium genus, along with shallots, leeks and chives. Long valued for their culinary uses, onions and garlic are also revered in traditional medicine for their health benefits, including some related to the prevention and treatment of asthma. Consult your doctor before using onions and garlic to treat a medical condition.
Onions contain a variety of anti-inflammatory compounds that may improve symptoms of asthma, according naturopath Mark Stengler, author of the book "The Natural Physician's Healing Therapies." High quantities of the antioxidant flavonoid quercetin are present in onions. A study published in 2011 in the journal "Bratislavske Lekarske Listy" found that supplementation with 20 mg per kg body weight of quercetin caused significant dilation of the bronchi in laboratory animals. Human clinical trials are needed to confirm these preliminary results. An average onion contains about 50 mg of quercetin, so eating onions on a daily basis may result in substantial preventive benefits for decreasing the frequency and severity of asthma attacks in some people.
Onions are included in a list of traditional medicines for treating asthma in the book "The Holistic Pediatrician (Second Edition): A Pediatrician's Comprehensive Guide to Safe and Effective Therapies for the 25 Most Common Ailments of Infants, Children and Adolescents," by Kathi Kemper, M.D., M.P.H.. Onions contain as many as nine different anti-inflammatory compounds, are safe to consume and rarely cause allergies or adverse reactions. The most effective dosages and types of onions for treating asthma are not yet known.
Garlic's warming nature makes it suitable for some forms of asthma but not others, according to traditional Chinese herbal philosophy. Ayurveda, India's traditional medicine system, recommends eating three cloves of garlic boiled in milk. Garlic taken together with apple cider vinegar and honey is a Western herbal remedy. The combination thins mucous and makes the lungs less congested and breathing easier. Take two cloves with one teaspoon of vinegar and one teaspoon of honey each morning before breakfast.
Onions and garlic have been known to cause asthma, particularly in occupational settings where workers are exposed to the dust from handling them, according to S. Buist, editor of the book "Respiratory Diseases in Women." Onions have also caused asthma in domestic settings, where exposures are much lower. Garlic and onions are related to asparagus, a vegetable that is also associated with asthma in some people, so if you are allergic to asparagus you may experience cross-reactivity with onions or garlic. Consult your doctor to make sure these foods are safe and appropriate for your use.