staff-writer from The Economist

Nor is America alone. For reasons still obscure, rates of childhood food allergy often rise as a country develops economically. A means of suppressing such allergies, rather than merely responding to them, would thus be welcome. And researchers at DBV Technologies, a French firm, are experimenting with one.

Allergies are inappropriate reactions by the immune system to molecules which, though harmless, it regards as hostile—perhaps mistaking them for chemicals on the surfaces of bacteria. In response it sends in waves of immune cells to attack them, and these cause the swellings and airway blockages. A sensible approach is to try to get the immune system used to these allergens, so that it ceases to see them as a threat. Past experiments have tried this, asking children to consume tiny amounts of peanuts, milk or whatever, and then gradually increasing the size of the dose. This works, but for obvious reasons needs specialist supervision, so is impractical on a large scale. Injecting controlled doses of allergen, as is done for hay fever, is also problematic. In the case of foodstuffs, such injections can cause severe reactions.

DBV thinks the answer is a patch that can be attached to a child’s skin. The firm’s device, made of plastic, is impregnated with an allergen (in the case of current experiments, powdered peanut protein). Water condenses under the patch and dissolves this protein, which is then absorbed into the skin’s upper layer and captured by Langerhans cells, which are part of the immune system. The Langerhans cells take the protein to nearby lymph nodes, which are responsible for mounting immunological responses. Unlike a hay-fever injection, this process means the allergen does not pass into the bloodstream. That reduces the risk of anaphylaxis. Like an injection, however, a patch delivers a controlled dose, so the immune system can get accustomed to the allergen’s presence, and thus cease to regard it as a threat.

 A recent trial of the peanut patch, conducted over the course of a year, involved 221 volunteers in 22 places around the world. Participants were given patches of one of three strengths, or a placebo. By the end of the year half of those who received the highest-dose patch were able to tolerate ten times more allergen than they managed at the beginning. Of those receiving a placebo only a quarter could do so. Moreover, as Jacqueline Pongracic, head of allergy at the Ann and Robert Lurie Children’s Hospital of Chicago, one of the centres involved, observes, the process seems safe. The worst reactions her team observed were localised rashes.

 read more at The Economist