Usually people are allergic to dogs with lots of hair. However, some people are allergic to dog saliva and urine. The best way to find out if you are allergic to certain type of dog is trying being around it for some time. You might need to spend at least a week with the dog you are purchasing and observe how you react to it. Keeping your dog in the patio, bathing your pet weekly, keeping your pet away from the furniture, washing your hands after touching your dog, and using allergy-reducing sprays might help. Nonetheless, no matter how much you wash your curtains or vacuum your floor, if your allergies are killing you the best thing is not to have a dog at all. Generally the symptoms involved with allergies are itchy eyes, red itchy skin or a rash, fever*, runny nose, and asthma symptoms. Children get more incidents of cold and asthma when allergic to dogs. There might be a type of dog you are not allergic to. The question is which one? You are on your own to find out. Good luck!
If people are that allergic to dogs that they'd have to keep them on the patio or away from furniture and bathe them once a week, they should not consider a dog for a pet. Dogs should NOT be kept outside unless in a covered kennel with access to shade/water etc. and they should NOT be bathed weekly, as the oils in the dog's skin and fur protect it and it's not recommended to bathe a dog weekly, or even monthly.