1. The problem statement, all variables and given/known data An individual suffered from a severe bout of parasitic infection. He recovered from this illness using some medical help, however he is affected by the same allergy in the next season of infection. The doctors are perplexed and would like to understand why the person is unable to display any immunity to the parasite. What can be the possible cause for the condition displayed by the individual? 2. Relevant equations Don't know. 3. The attempt at a solution Is it the parasite has modified and macrophages are not able to detect this? But here in question it is mentioned that individual is affected by same allergy.