Is my neutered dog infected?

The pattern of the redness clearly indicates at least strong skin irritation, if not infection. Your dog clearly indicates that he's in pain, so the pain is rather severe, too. (Dogs usually hide mild pain and only show symptoms if the pain is strong.)

Please try contacting your usual vet by phone and explain the situation. Maybe they'll treat your dog as an emergency and see him today. If not, try finding a different vet that's open today.

If all things fail, try to get a dog-safe painkiller at the pharmacy. Ibuprofen can poison your dog. Dog-safe medications (WebMD) include:

• carprofen (Novox or Rimadyl)
• deracoxib (Deramaxx)
• firocoxib (Previcox)
• meloxicam (Metacam)
• Only if you cannot get any of the above, use Aspirin because it has more side-effects

Read the package leaflet for the appropriate dosage for your dog. Always offer him food when you administer a pill to avoid side effects in the stomach. Treat him until the redness lessens or you can see your vet. If he doesn't swallow the pills, you should hide them in a small piece of wet food, hotdog sausage or cheese. The goal is to have the dog swallow the treat without even chewing so he won't notice the pill.