Why does Frog Fuel Ultra give me hives or making my skin tingle?

This is more than likely due to the beta-alanine.  The pins and needles feeling you get on your skin after taking beta-alanine are referred to as paresthesia.  It is a harmless side effect and is not an allergic reaction or an inflammatory response. It is caused by MAS-related and sensory neuron's response to the beta-alanine.

The theory is that beta-alanine activates G-protein-coupled receptors, which are responsible for transmitting signals throughout your central nervous system, and especially on the skin.

In other words, the amino acid fires up your nerve endings in a way that causes that beta-alanine to tingle and itch, but not enough to cause actual pain.

Beta-alanine acts at the cellular level to keep the pH within the muscle from getting too acidic, which contributes to fatigue. Therefore, beta-alanine delays neuromuscular fatigue, which gives performance benefits. 

Note:  If you are having trouble breathing, contact your nearest medical facility.  This may be an indication of an allergic reaction to something else.  Beta-Alanine is not known to cause an allergic reaction.