i'm surprised your husband has been signed off work, and for so long too. rosacea (acne rosacea to give it it's full title) is not an infectious disease, more an embarrassing skin condition causing facial redness and bumps, but nowhere near as unpleasant as some of the more severe skin conditions like psoriasis or excema. i have suffered with it, on and off, for 35 years. a course of oxytetracyclene usually settles it down pretty quickly, but oxytet may need to be taken for quite a while to prevent it recurring.
google it and you'll find lots and lots of sites where it will be explained in detail.