Evidence from:
Strannegård Ö, Strannegård I-L, Allergy (2001) Vol. 56 #2, p.91-102.
Review of research into the causes of the increasing prevalence of allergies. Many reasons investigated, but none proven.
Author proposed that a major factor is a lower “microbial load” when young compared to good old days, i.e. today’s (perceived) higher hygiene standards present less chance for the immune system to be stimulated regularly at a young age (less stimulation of T-helper¹ cells). This is suggested to prevent ‘hyperactivity’ later in life.
Comment
This may be one of many possible factors. However nothing was proven.
Innocent causes of allergies should continue to be monitored.