No, he tests it with his screwdriver

The Doctor scanned the water and from the reading his sonic screwdriver gave, he knew that there were some very powerful endorphins in the water - the result in making humans incredibly horny.

He turned to look at Rose, who was now very aroused and starting to strip.

Rose was now wearing just her bra and panties, the rest of her clothes being discarded on the floor. The matching black lace underwear barely concealed her gorgeous body. The Doctor could clearly see her hard nipples and bald pussy through the lace.

The Doctor watched the striptease with increasing excitement.

As Rose finally finished stripping, and was now naked, the Doctor started to undress. As he removed his clothes, Rose leant against the cave wall, and slipped two fingers into her already wet pussy. Her other hand tweaking her hard nipples.