Have animal allergies and have been around a cat and dog. I had an itxhy eye whuch has now become vwry puffy and red. Can I take 20mg f loratadine?

Allergies. Maximum recommended daily dose of loratadine is 10mg. Consider getting some over the counter allergy eye drops. Over the counter nasal steroids can also help eye symptoms (example of one is fluticasone) since the nasolacrimal area is so close . .
Benadryl (diphenhydramine) Is the recommended antihistamine. If you have airway or breathing problems, call 911. All the best.
Puffy eye. Go to an ER or urgent care for immediate doctor attention . In the mean time take 10 mg loratadine . If you take 20 that is overdose and you may develop side effect of the loratadine.