Die off reaction occurs when the change you implemented (in this case addition of antifungals, anti candida diet, etc) begins to take effect in your system, killing off the yeast. This "die off" of the overgrown organism typically results in large amounts of toxins released into the blood stream, initially forcing the immune system to overwork to remove the waste. Typical symptoms of this die off reaction are sore throat, general weakness and other cold symptoms. Again this a positive reaction because your body is releasing unwanted waste. In order to minimize die off symptoms one can do general cleansing (bowel cleanse, liver flush, etc) to make sure the elimination pathways are open.
Unfortunately allergic reactions to some of the foods or supplements you begin to add to your daily routine can have similar symptoms so it becomes tricky to distinguish them.
Mike