My allergy to shrimps

I know I have allerge to shrimps, but I still eat them.
The problem is 60% of the time, I will be fine.  Rest of the time, my allergy will develop. 
I have tried to observe the differences when they happened, like what other food I had at the same time, whether I was tired.  But I have not found any systematic differences.

Could someone tell me why there is the difference?  Thanks in advance,

所有跟帖： 

• do not take them together with anything high in Vitamin C such a -要吃龍利魚 - ♀ (0 bytes) () 08/01/2013 postreply 13:40:58

• 回複：do not take them together with anything high in Vitamin C suc -要吃龍利魚- ♀ (0 bytes) () 08/01/2013 postreply 13:41:51

• do not take them together with anything high in Vitamin C such a -要吃龍利魚- ♀ (0 bytes) () 08/01/2013 postreply 13:42:24

• please read together with the one below --such as orange juice -要吃龍利魚- ♀ (0 bytes) () 08/01/2013 postreply 13:43:35

• 你得搞一個多因素調查 -滿地找牙- ♂ (208 bytes) () 08/01/2013 postreply 14:59:07

• 同意。還有幾個問題： -欲千北- ♂ (418 bytes) () 08/01/2013 postreply 15:17:25

• thank you to all -joeyli- ♀ (503 bytes) () 08/01/2013 postreply 17:23:40

• 謝謝回複。非常理解輸入問題。我打中文也慢。繼續問題 -欲千北- ♂ (140 bytes) () 08/01/2013 postreply 18:47:28

• 你這種過敏叫水土不服，本地產不發，看清產地能避免 -Wafik- ♀ (187 bytes) () 08/02/2013 postreply 12:54:00