My Dog Is Losing His Hair On His Tail. There Is A Small Red Patch That Looks Irritated And Is Itchy. Is There Anything That I Can Do To Relieve The Itching.

It is always best to know what you are treating before applying medication.  There are several things that are zoonotic (can be transmissible to people.  Common skin conditions include ringworm, hot spots (moist dermatitis), mites (some of which can be transmitted to people), allergies (flea, environmental, food), and foreign body migration (foxtails, cactus spines, etc). 
Also when the skin is damaged and dogs start self-mutilating (licking, chewing) it opens up the wound for secondary infection (yeast, bacteria, mites). 
It would be best to work with your veterinarian to rule out causes of dermatitis and create an appropriate treatment plan.  Initial tests will include a skin scrape to look for mites, skin cytology to identify infection, and a fungal culture for ringworm.
Before your appointment you need to stop your dog from chewing this area.  This best way to do this is with an Elizabethan Collar--these are available through pet stores or veterinary clinics.  Topical cortisone may reduce itching but can make certain conditions like ringworm and mites worse.

Our dogs developed different allergies to plants in the back yard and we used Savlon to clear it up and removed the plants also. Both of them had lost fur and had red itchy patches. Your dog may try and lick the Savlon off so rub it in as best you can. If it starts to spread after a week or so you may need to get cortisone injections at the vets,but try Savlon first

It sounds like he has ringworm, if so , now I'm not a vet, but this has worked for me if you can't take him to the vet, try putting Lamisil on it. It is an over the counter fungus relief and it cures ringworm,if that is what he has.

This is commanly known amongst Pitbulls. Both of my dog's get it from food that doesn't have enough oils in it. I suggest you start feeding him Orogen 6 fish diet. It's pricy but your dog will love it. As well get a bee's wax stick found in pet stores and apply onto the spot....this will help.

It could be something called hot spot eczema.
 
---} read about hot spots here {---
 
And like the others say If your dog or cat is sick, call your veterinarian! 
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I know exactly what that is, it's mange or hot spot. It's only a hot spot if puss comes out but I'm sure it's mange, my dog has it.