I used to get asthma as a child but have had no trouble for years until last weekend at a barbecue when I got so bad I had to go to the hospital. I had quite a few pickled onions that I don’t usually eat, and someone reckoned these could have brought on the attack, so I want to know if this is true?
Yes, this is quite true. From your story of being free of asthma, it sounds as though the pickled onions were responsible for triggering the adverse reaction. The chemical additive, metabisulphite, used in the pickling process is the problem, not the onion. Metabisulphite has become recognized only fairly recently as a common cause for food sensitivity reactions, especially asthma.
Metabisulphite is present in a wide range of preserved foods and is usually, in the U.S., not listed on the contents label. Many people must have reactions and fail to make the connection with what they have been eating or drinking. As well as pickled onions and pickles, metabisulphite may be found in some fruit juices, soft drinks, cordials, wine, cider, sausages, frankfurts, cheese and meat mixtures and pastes, dried fruits and vegetables, frozen prepared vegetables especially potatoes, prepared “fresh” fruit salad and potato crisps.
For someone who had serious asthma which could be provoked by metabisulphite, it could be life-threatening to eat some of these foods. There is an urgent need for proper specific food labeling to protect a large number of people.
You should avoid pickled onions, of course, and test yourself with the other foods. People who have severe asthma requiring daily medication should not try this themselves. They should ask for a referral to a specialist respiratory physician or allergist so that testing can be done in a controlled safe conditions.
There are a variety of chemical compounds in addition to metabisulphite that can cause sensitivity reactions (often wrongly called food allergies) in various systems of the body as well as asthma in this case. Some of these other problem chemicals are monosodium glutamate, used in seafood and Chinese food, nitrates, tartrazine, azo dyes, and salicylates.
If by doing a bit of detective work you can link eating certain foods with recurrent symptoms such as asthma, hives, dizziness or nausea, you may well improve your health by avoiding the particular chemical responsible. The message is to eat simple, fresh foods where possible, and avoid highly processed chemical foods.