I have recently brought some old books home from a sub tropical region. As I was going through them, I seem to grow itchy spots. I don't know if there is any invisible stuff in them or just allergy from the old paper. The books were stored in very old humid environment. What can I do to deal with this.

You may have heard the term "booklice" before. Likely what you have run into is a nearly microscopic insect called "psocids". They require high humidity and can feed on paper and bindery glue. To kill them without damaging the books, put the books in a sealed container with mothballs for 72 hours. Don't pack them tightly, the napthalene vapors need to circulate all through the books to find the bugs' hideouts.