Recurrent Petechiae in 1 year old

Hi-  I have a 14 month old son who has had recurrent petechial rashes since he was 5 months old. On a daily basis he has scattered petechiae from his neck to his groin- most severe around his neck.  He has been to two hematologists, who found nothing abnormal in his bloodwork (other than a lower than normal anc for about 8 weeks). He has been to a dermatologist 3 x who confirmed that he does have petechial rashes, but did not have an explanation. We are waiting for an appointment with a pediatric dermatology specialist (3 month wait to see him- our appointment is for mid- september). Yesterday my pediatrican found petechiae on my 3 year old daughter as well- a cbc and pt/ptt were done, however we don't have the results yet. We have never before found petechiae on my daughter, and there were just a few spots (my son always has many spots)  What could be the cause of recurrent petechiae?  Both the hematologist and dermatologist we have seen have said that they have never before seen a child with recurrent petechiae with no apparent cause.  
My children are fair skinned irish kids. I get petechiae from throwing up, but I assume that is pretty normal. There is no one else in the family who gets petechiae for no reason. My husbands grandmother had factor 7 deficiency, however my son's factor 7 is fine according to the hematology work up.
Is there a dermatological explanation for this? I am stressed out and worried about my children- although I understand that if there was something seriously wrong it would have played out by now, and I am comforted by the blood test results.  

[Alan Rockoff, MD]

Like the dermatologist and hematologist who saw your children in person, I don't really know what your kids have.  If both kids have it, this at least raises the question in my mind of insect bites of some sort.  Perhaps a visit from an exterminator might be of value.  With no blood abnormalities found, I can't think of any internal or serious conditions to consider.

Best.

Dr. Rockoff

[BusyMommy613]

No, definetly not insect bites. Every doctor they have been to agrees that they are petechiae.

thanks.

[Pum]

Are they playing rough with each other? Sometimes you can get this from injury or I have had them after an allergic reaction or rubbing (socks when jogging). Is it just in the area where he wears clothes? Maybe an allergy to what he is wearing?