Is it warm enough for winter?

It is a single-layer cotton tee, so it works best as a base layer under a shirt, jumper or jacket. On its own it suits mild days.

Will the elbow patches hold up to rough play?

The patches are stitched over the elbows, the spot where long sleeve tees usually wear through first. They add a layer of fabric there, though the rest of the sleeve is ordinary cotton.

Does the slogan wash off?

The slogan is embroidered rather than printed, so it does not peel or crack the way a print can. Wash inside out to protect the stitching.

Is the cotton safe for sensitive skin?

It is 100% organic cotton with a ribbed neck, and the description makes no mention of synthetic blends. Breathable cotton is a reasonable choice for kids with sensitive skin.