Typically, someone who is in agreement with you will smile and nod as you speak. (Disagreement shows up in compressed or pursed lips, clenched jaw muscles, or a head turned slightly away, so eye contact becomes sidelong.) But smiles are often used as a polite response and to cover up other emotions.
The UCL team discovered that MIP-1a plays a key role in the early stages of an allergic response within the clear membrane that coats the inner surface of the eyelid and outer surface of the eye, known as the conjunctiva.