Ive been using the OISD list for myself and family members for the past couple of years without issues. It’s specifically made to to be unnoticeable, by whitelisting hosts that would cause issues.
One thing to note is that it’s not a full replacement for adblockers, as DNS blockers can only block full hosts and not all ads and tracking are served from dedicated hostnames. Things like YouTube ads will be unaffected by DNS based blocking. It does really make a difference, though, including for apps with banners.
That makes sense, it’s usually not the hairs that people are allergic to. It’s a protein in their saliva, urine and skin flakes. Hairs could be covered with saliva and/or skin flakes, so in that sense I guess people might still react to the hairs, but a naked cat can trigger an allergic reaction too.