The red bumps can be easily explained by the simple fact that excess iodine being pushed out of the pores irritates the pores. The irritation leads to inflammation, thus little red bumps. A white head is only going to form if there is an immune reaction against a pathogen. The white pus is white blood cells that die fighting the pathogen.
And again if it were bromide being pushed out of the skin then why don't the halogens fluoride and chlorine that we are exposed to in abundance and that both displace bromine cause the same problem? If bromine being pushed out of the skin was causing this then nearly everyone would have severe acne considering how much of these halogens we are exposed to on a daily basis.