allergies or fungus

My baby is ten weeks old at the present.  At two weeks of age he began to break out with a rash over his entire body.  I took him to his regular pediatrician and he tested him for scabies and staph infection.  Both of these came back negative.  The doctor prescribed antibiotics and it help the rash to fade but returned after the medicine was finished.  We then took him to a dermatologist and he thinks that is is a fungus.  He thinks that someone has held the baby and has given this to him. He doesn't want to do a biopsy because the baby is only ten weeks old.  When the rash is at its best there will be places that actually look like an ant bite when it has a white head on it but it is not.  Do you have an idea of what this could possible be?  Do you have suggestions.
Thanks,

[Dr Santos]

Hi,

It is good that your baby was negative for both staph and scabies. Do you have family history of allergies? This may be passed on to your baby as well and the lesions could be allergic reactions. Are there other signs or symptoms present? It is important to refrain other people from touching or carrying him to avoid passing any sickness.

It is also highly recommended to have him breastfed to make his immune system stronger. If it still persists, a referral to a pediatric dermatologist may be helpful.
Take care and kisses to your son.