Cheryl/fern,
I agree with Yvonne. I also think it's a combination of perspiration and saliva. I also don't use powder as it clogs the pores. I usually don't do/apply anything. Just keep the area clean and dry as much as possible and let it heals itself.
Yvonne,
I am also using J&J diaper cream. Can get in Malaysia. You want? Can get for you next time I go.
Fern,
You can't just listen to your doc that egg yolk is okay for your son. How did you first introduce it? Did you apply the 3-4 days waiting rules when he takes yolk at the very first time? Same as the ikan bilis and silver fish. If first time okay, then your son is not allergy to these food. If you didn't follow the 3-4 days waiting rule when you first introduce the food, then stop all these food, and start by introducing 1 by 1, and use the 3-4 days waiting rule.
And I think rashes due to allergy is not only on the chin and neck, it shows on the hands as well?