An Epidemic of Absence (2012) by Moises Velasquez-Manoff (MVM) is a book that looks in the rise of auto-immune diseases and the hygiene hypothesis. MVM himself has a alopecia, premature baldness and a number of allergies himself and clearly thinks the hygiene hypothesis has merit.
Since the 1960s in the developed world allergies and auto-immune diseases in general have gone up substantially while they have not done so nearly as much in less hygienic populations in the developing world. There is definitely something in the idea. Comparisons between cleaner city dwellers and country dwellers in the developing world also support the idea. Also East and West Germany had differing levels of these diseases with the slightly dirty and also much more polluted East having less.
The book has a bit of narrative structure with MVM discussing worms and the scientists who have a great interest in them and toward the end MVM uses worms on himself, getting some benefits but sizeable side effects.
The book is a little too enthusiastic about it but it’s still a thought provoking, if overly long, read. MVM does have some scepticism about the wildest claims and definitely has a point though.