What Causes Sweating On Head In A Child?

hello doctor, i have a baby boy 5 months old and he often sweats on his scalp (all over the head). it is more seen after drinking milk and when he cries. born on time no complication during delivery every thing is fine . recently developed fever 103 degree farenheit. after blood sampling found his potassium levels are high at 5.3 mm. what could be the reason for head sweating?