Thanks for the query.
This can be due to two things
1. allergic reaction
to contact with fumes of sulphuric acid.
2. allergic reaction to the boots he is wearing.
Ask him to apply a mild steroid
A leave from work for few days will be good
Please meet a dermatologist
if it persists.
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.