A lot of research has been done where hookworms are used to treat allergies. The main concept being that a modern immune system is bored without an enemy to attack and then attacks innocent cells.
Say the body is America and the immune system is America's defence force. The immune system is needed when dangerous pathogens appear, in the same way that American troops are needed to defend against enemies. If America is in no war and all its troops are recalled without downsizing the military, these troops will get bored and start identifying innocent people as enemies. It might shoot down a trainee pilot from Canada when entering American air space. This plane falls on a city and damages property or may start a fire in America. In the same way, the immune system may become bored when there are very few pathogen and starts attacking molecules that are not dangerous. Just as the defence force can be trained to identify russian fighter aircraft on a radar, so the immune system can be trained to identify pathogens correctly by means of vaccinations. In the extreme case, the defence force might attack the poor Canadian with an atomic bomb so big it destroys the whole continent. In the same way an allergic reaction can kill the person.
Now in Helminthic Therapy http://en.wikipedia.org/wiki/Helminthic_therapy
, the hookworms are used as a perpetual enemy in the same way that America might used Afghanistan/Vietnam/Iraq. This causes a constant drain of blood, but when controlled, it may improve the health of the body overall.
Dogs are carriers of hookworms and the benefits of hookworms and allergies has been known for a long time, so in my opinion, this article is old news.