HI, thanks for using healthcare magic It is quite likely that the occurence of the fever at the time when the cream was applied is coincidental. He may be coming down with an acute infection,the most common is the common cold or another viral illness. Hydrocortisone cream is not associated with fever. There is very little systemic absorption and also, it is an anti inflammatory agent which means that it should decrease in responses such as fever. The ferrous sulphate is also not usually associated with these symptoms. You may want to consider speaking to his doctor. I hope this helps