I agree with what Karen B said. Change the diet is a great start. Cow's milk is VERY bad for the body. It's very mucus forming. Just getting rid of that alone will help with colds/allergies, etc.
Another thing that I would do right now is go to Wal Mart or your local health food store and get something in a box called Emergen-C. It is a fizzy drink mix powder that has 1000mg of Vitamin C in one packet. When our 2yo gets a runny nose, which isn't often compared to other kids (we are very big handwashers), I give her two packets a day in her sippy cup with water. There are many flavors to choose from. You'll find more flavors at a health food store, but Wal Mart should have 2 or 3. My 2yo likes the Super Orange and the Raspberry..she does not like the Tangerine...I guess it's more tangy. Anyway, this keeps her runny nose away. I usually wait a few days and then stop giving it to her and it's gone. Other times, the following day after having not given it to her, her runny nose starts back up, so I resume the Emergen C and within a couple of hours, her nose stops running.
Allergies are typically due to an immune system problem. Now, as far as the rest of the symptoms...what to do? Well, I have a child...my oldest that had animal allergies bad when he was younger...since then it isn't so bad, but he can now actually stay within a home during the day with animals, but just can't sleepover. What did we do? Read the following excerpt first and I'll tell you the dramatic results. (you can find the following herb at www.herbsfirst.com or www.worldhealthdepot.com....the latter is cheaper) The formula is called Kid-E-Soothe
"This formula was designed to calm yet strengthen the body’s immune responses. Oftentimes, we believe that we are allergic to certain foods, plants or animals, but in reality our immune system may be just overreacting. This simple combination of Marshmallow root and Astragalus has made life easier for those who suffer from allergies, hay fever, asthma, rheumatoid arthritis or any hyperactive immune response. This extract is in a base of 100% pure vegetable glycerine with natural cherry flavoring."
Now we found out our son had allergies to animals when he was about 2yo. Oh my goodness, within minutes he looked like he was diseased! He had red welts and spots all over him, lips swelled, eyes swelled shut, breathing was difficult, he was itching all over and going beserk, I might add. I had to rush him home many times due to animals in the house of people I visited and put him in a bath of essential oils to calm him down. It was awful for him. I remember one time we went to a friends house and I knew that she kept her dog outside, but this time she had a cage inside the house because they were doing something outside. Anyway, the dog was no where around, but my son walked over to the cage and touched it. That's it and I was running out the door back home. He was going beserk and crying all the way. You should have seen him. After that, I stopped going over to friends house with animals inside the house....I couldn't put him through that anymore.
Okay, I just wanted to explain to you how bad it was before I told you what we did. I found Immucalm. He was 4yo by now and knew how to swallow capsules, so we used the capsules instead of the extract...besides, he didn't like liquid 'medicine'. It was AMAZING! The first time we tried this out, I knew that I would be visiting a friend who had animals in her house. So a week ahead of time, I started him on Immucalm. When we went to her house, he had NO reactions at all! Would you like to know how many animals are in her house? 6! 2 dogs and 4 cats. My son is allergic to both, including rabbits, horses, etc. He had no reaction at all whatsoever! I was totally amazed. So, if I knew ahead of time that we would be visiting (we tried to resume a life again of visiting other children, etc.), he would be on it ahead of time. I did not give it to him all the time, even though that wouldn't be a problem because these two are safe herbs. Now, he doesn't take it at all unless it's after the fact. He is now 10yo and can now walk into my friends house with 6 animals without having taken the Immucalm. She keeps her house really clean (you wouldn't even know she had animals, if you didn't see them). But he still can't stay overnight. He has come a long way from what used to happen. But he still has allergies. Unfortunately my 10yo is a very picky eater and doesn't eat too much more than peanut butter sandwiches.
Anyway, thanks for reading if you actually made it this far. I just had to tell you about what has helped us.