Does the military obtain medical records during the enlistment process?

Show symptoms during MEPS and they will do the research and find it. Show symptoms within a few weeks or months and they will find it and you will be charged with Fraudulent Enlistment, a Federal felony.

Lying will only get you in trouble.

Here's the thing. They won't look unless you give them reason to. You aren't that important (except if you are getting a security clearance) and they aren't going to dive into all of your records because it's too expensive, and the legal process to get your medical records isn't too fun for them. However, the minute you start expressing the symptoms for what you have, they will look to see if it is a pre-existing condition so they don't have to pay for your condition and throw you out of the military with a fraudulent enlistment or a punitive separation. Not pretty, but I've seen alot of Marines leave things out of their record. It's a gamble.

Yes, of course.

b. Atopic dermatitis (691) or eczema (692), with active or residual lesions in characteristic areas (face, neck, antecubital, and or/popliteal fossae, occasionally wrists and hands), or documented history thereof after the age of 8.