About 30 percent of Americans believe they have food allergies¹（食物过敏） . However, the actual number is far smaller, closer to 5 percent, according to a recent study commissioned by the National Institute of Allergy² and Infectious Diseases (NIAID). That's due in large part to the unreliability（不可靠，不安全） of the skin test that doctors commonly use to test for food allergies. MIT chemical engineer Christopher Love believes he has a better way to diagnose such allergies. His new technology, described in the June 7 issue of the journal Lab on a Chip, can analyze³ individual immune cells taken from patients, allowing for precise measurement of the cells' response to allergens（过敏原） such as milk and peanuts.

Using this technology, doctors could one day diagnose food allergies with a simple blood test that would be faster and more reliable than current tests, says Love, an assistant professor of chemical engineering. "With a large number of diagnoses, it's ambiguous（模糊不清的） ," he says. "A lot of times it's almost circumstantial whether you're allergic⁴ to one thing or another."

The NIAID study, published May 12 in the Journal of the American Medical Association, found that in the United States, 6 to 8 percent of children under four, and 4 percent of people five or older, have at least one food allergy. Milk, peanuts, eggs and soy（酱油，大豆） are among the most common allergens.

Food allergies occur when the body's immune system mistakes a protein in food for something harmful. This triggers an allergic response that can include rashes（发疹） , hives（荨麻疹） , difficulty breathing or gastrointestinal（胃肠的） distress⁵. Some allergies can provoke（激怒，驱使） life-threatening anaphylactic shock（过敏性休克） , which requires immediate⁶ treatment.

Patients suspected of having food allergies usually undergo a skin test, which involves placing small quantities of potential allergens under the skin of the patient's arm. If the patient's blood has antibodies（抗体） specific to that allergen, immune cells will release histamines（组织胺） that cause itching⁷（痒，渴望） and redness in the spot where the allergen was placed.

Doctors can also perform blood tests that directly measure the presence of particular antibodies in the patients' blood. However, one drawback to both of these tests is that the presence of antibodies to a particular allergen does not necessarily mean that the patient is allergic to that substance, leading to false positive results.

Love's new technology, developed with funding from the Deshpande Center for Technological⁸ Innovation, the Dana Foundation and the NIAID, takes a different approach. Instead of detecting antibodies, his system screens the patient's immune cells for small proteins known as cytokines（细胞因子） . Immune cells such as T cells produce cytokines when an allergic response is initiated⁹, attracting other cells to join in the response.

To perform the test, blood must be drawn¹⁰ from the patient, and white blood cells (which include T cells) are isolated¹¹ from the sample.

The cells are exposed to a potential allergen and then placed into about 100,000 individual wells arranged in a lattice（格子） pattern on a soft rubber surface. Using a technique known as microengraving, the researchers make "prints" of the cytokines produced by each cell onto the surface of a glass slide. The amount of cytokine secreted¹² by each individual cell can be precisely¹³ measured. For food-allergy testing, the cytokines of most interest are IL4, IL5 and IL9.

The "gold standard" for diagnosing a food allergy is to see what happens when the patient is given the food in question (in a controlled setting, to ensure safety), but that is not often done outside of allergy research clinics, says Assa'ad.

Love is now working with Dale Umetsu, professor of pediatric（小儿科的） immunology at Children's Hospital Boston, on a project they hope will pinpoint¹⁴ the relationship between cytokine activity and allergic reactions. In that study, children with milk allergies are being given small amounts of milk to desensitize（使麻木，使不敏感） their immune systems to the milk. Using the new technology, the team is tracking how the responses of the patients' cells change as the patients undergo treatment.