According to multiple sources, the rarest allergies include:

1. Water Allergy: Aquagenic urticaria is a rare condition that causes itchy and painful hives to break out whenever the sufferer comes into contact with water. Changing the water temperature has no impact on the allergic reaction, and there is no effective treatment.

2. Sun Allergy: Photosensitivity, also known as a sun allergy, causes individuals to develop hives on their skin when exposed to sunlight. The most common areas for a sun allergy reaction to occur are the suprasternal notch, behind the hands, outside surfaces of the lower legs, and outsides of the arms.

3. Red Meat Allergy: This allergy is caused by a tick bite and can cause hives, swelling, and even anaphylaxis when the person eats red meat. The allergy is caused by a sugar called alpha-gal that is found in the ticks saliva.

4. Exercise Allergy: Exercise-induced anaphylaxis is a rare condition that causes hives, difficulty breathing, and even anaphylaxis during or after exercise. The exact cause is unknown, but it is thought to be related to changes in body temperature or dehydration.

5. Money Allergy: This allergy is caused by a compound called nickel sulfate found in coins. It can cause hives, itching, and even anaphylaxis when the person comes into contact with coins.

It is important to note that while these allergies are rare, they can still occur anywhere, including in New Jersey and Pennsylvania.