hello and welcome,
it can be due to mercury toxicity which is also called as pink disease/acrodynia/swift's disease.
but the final diagnosis can be made only after getting the result of blood mercury level investigations.
some primary measures to be taken are-
and maintenance of vital functions-ensure patent airway,adequate ventilation,give artificial respiration
as needed,maintain bp and heart beat,maintain body temperature,maintain blood sugar level.
2.termination of exposure or decontamination by removing the patient to fresh air,induction of gastric lavage.
3.prevention of absorption of ingested poisons.
4.hastening elimination of the poison by inducing diuresis.
hope your son get well soon.