Tick bites or any contact allergy makes the penis to swell up because of the fluid getting accumulated underneath the skin.
If there is no pain and red color, he only requires antihistamine like Benadryl half teaspoon twice daily.
If the swelling is increasing and he has pain and if there are wheals developing in other parts of the body, you need to take him to his doctor for an injection of steroid and oral antibiotic to control secondary infection.
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