Is the I Watch Hypoallergenic?

I am not basing my answer on any chemical analysis of the watch band, but on my wearing it for several days. The answer (at least for me) seems to be NO, it's not hypoallergenic. The first few days were ok because I was in an office most of the time and my skin was relatively dry. Today I am doing work around the house and getting a bit sweaty. After about two hours under these conditions with moist skin, I have gotten a large red welt right under the metal disc that's on the underside of the clasp (pictured here).

The welt is very itchy and is typical of other allergic dermatitis reactions I've gotten in the past from wearing metals containing nickel. I have put a piece of tape over the metal disc for now to see if that helps, and I loosened the band just a bit.

I've not had a reaction to the underside of the watch body, but that's on the top of my arm where I have a nice layer of fur. Hopefully I'll be okay there.

I didnʻt even think of the nickel issue (which is also very relevant for me since Iʻm badly allergic to nickel).

It looks (on the product info pages of Apple Watch) like the watch part material listed is316L Stainless Steel, so that is probably what touches your skin.

Stainless Steel - Grade 316L - Properties, Fabrication and Applications(UNS S31603)

Chemical Formula

Fe, <0.03% C, 16-18.5% Cr, 10-14% Ni, 2-3% Mo, <2% Mn, <1% Si, <0.045% P, <0.03% S

10-14%... for allergy safety, Iʻd give it a pass, unless you can find a way to wear it over a sleeve or fabric, or find a solution that works for you.

What about the Aluminium version - Sport watch?

It looks like apple has now posted a page referring to the subject.

Wearing Apple Watch - Apple Support

"Apple Watch, the space gray Apple Watch Sport, the stainless steel portions of some Apple Watch bands, and the magnets in the watch and bands contain some nickel. However, they all fall below the strict nickel restrictions set by European REACh regulation. Therefore, while nickel exposure is unlikely to be a problem, you should be aware of the possibility in case you're susceptible to nickel-related reactions."

i read an article that people mostly experienced allergic reactions due to the stainless steel clasp or sometime to the silicon type watch bands, here I found a site with hypo allergenic watch bands listed, http://www.smartwatchappcenter.com/hypo-allergenic-apple-watch-strapsbands.html but if you want to make it sure you can just go to Apple Store and ask the attendant if there are Apple watch band that is hypo allergenic