slight bump becomes blister

My 4 month old has had a small mole-like, light brown in color, bump on his chest (right below the chin area) since he was about a month old. You could barely feel it if you rubbed your finger across it. As he has grown over the past 3 months, the bump has grown in diameter as well. I took him yesterday for 4 month shots and pointed it out to his pediatrician who, in return, said that we would watch it over time. While feeding him this afternoon, I removed his shirt and I noticed that the spot was now a raised blister filled with liquid. I bathed him, and while rubbing him with lotion the blister popped, but no more than an hour later there was a blister there again. Any idea what this may be?

[Bhupinder Kaur, MD]

Hello,
If the mole has been present for quite some time then any change in the mole should always be examined by a dermatologist. As a thumb rule, whenever you notice changes in the mole's/mark’s color, height, size or shape, you should have a dermatologist evaluate it. You also should have it checked if it bleeds, oozes, itches, appear scaly, or become tender or painful.

It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.