Sun cream allergies!

Charlotte

My son aged 6 has had a reaction to sun cream as I put some on him 3 days ago as weather heated up, he had a rash yesterday were I had applied it a few days ago and he still has it today after I soaked him in a bath to clean his skin through. We are set to go away in 4 days so GP wouldn’t get back to us in time so I was wondering if anyone knew of an allergie free sunscreen we could buy? We are giving him antihistamine too

Many thanks