In mild cases, which constitute the majority
of allergic reactions to vaccines, cats may develop hives, itchiness, redness and swelling of the eyes, lips, and neck, and mild fever.
In very rare cases (1 - 10 of every 10,000 vaccines administered), cats can have
allergic reactions to vaccines.
Answer: It's possible to itch and lose hair as
an allergic reaction to vaccines but it's rare.
It is also possible that he may have
an allergic reaction to the vaccine which can result in hives or facial swelling.