Many Judges do not understand the severity of Exema.
You might want to consider, giving the Judge, by wayof declaration, a desription of what Exema is.
You should consider filing a letter from the child's doctor regarding exema.
Then file your own OSC regarding a change of the orders, based upon Father's failure to adequately care for the Child's exema.
Please note that this answer does not constitute legal advice, and should not be relied on, as each situation is fact specific, and it is not possible to evaluate a legal problem without a comprehensive consultation and review of all the facts and court pleadings filed in the case. This answer does not create an attorney-client relationship
Start documenting your son's condition by taking pictures of him before and after the weekends. More importantly, take him to his doctor for advice and request a letter stating that he is not receiving the proper amount of medication as advised. Furthermore, see if you can schedule a visit with doctor, you and the ex to educate him on the issue. Hopefully, he may learn to take proper care of your son. However, if he fails to make the appointment, or fails to follow through on the instructions provided, then you will have plenty of evidence to file your order to show cause to modify his visitation until such time as he can prove to be fit to properly care for your son.
If you have any question please do not hesitate to contact me directly at 909-635-2023.