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Dust mites live everywhere. Protein in dust mite poop can cause allergies.
There's a thing called "total allergy syndrome" where such people who have this, seem to be allergic to pretty much everything. However, there seems to be controversy as to whether the suffering is from a psychological context or not...something like a fear of chemicals everywhere.
There's also food allergies. Around 4% of adults have it.
Always remember that you must have previous exposure, because the body reacts by producing these antibodies. However, the body produces antibodies to substances that are not harmful, then during the subsequent times, the antibodies will appear on something.
Gelatin can be used as stabilizers in vaccines. Royal jelly can be contaminated with pollen. Such instances can easily lead to allergic reactions.
A sign that allergies are increasing are from the doubling of asthma rates since the year 1980.
Another thing to note is that as our population increases, the introduction of an array of substances in life becomes wider. Around 80,000 chemicals since the 1940s have been introduced!