and itching is a common
side effect of Thiamzole and this itchy skin rash
that your mother is having can be due to hives as a result of the side effect of this drug. For such hives, first of all the medication
needs to be changed to some other drug. Then the primary treatment is by oral antihistamines. The most potent antihistamine, however, is probably the anti-depressant doxepin. You can apply an anti-itch cream or lotion
to the affected area.