While using chlorine in a spa is not recommended it is commonly used.  If you are allergic to chlorine then use bromine.  Chlorine loses it's effectiveness in hot water.  Using chlorine is also good for shocking bromine or your spa water. 

NOTE:  Salt water chlorinators are also a great alternative to buying and using chemicals. There is not taste or smell and they keep your skin and hair soft while using the spa.    HIGHLY RECOMMENDED