It looks very odd. I found this explanation on The Express, via google:
What is the patch on Mrs May’s arm?
Mrs May arrived wearing a sleeveless floor-length crimson dress with a slit up the back, paired with red heels - a welcome change from power suits and leopard print shoes.
Turns out the patch on her arm is a diabetes monitoring patch.
It’s a small white circular patch which monitors blood sugar levels and lets her know when she needs to inject insulin.
She said last year: “I am a type one diabetic. That means when I eat, I have to inject insulin, which I do.
“I will be injecting myself four or five times a day… You just get into a routine.
“You depend on that insulin and you just build that routine into your daily life.”
“The crucial thing to me is being a diabetic doesn’t stop you from doing anything.”
Web Designer / Developer. Currently working on Paphos Life.
Living in Polemi, Cyprus with my wife and daughter.
And just to clarify something, when I said "on the Express, via Google" it wasn't me saying "you should have googled it" Rather, I was saying "I don't normally use the Express website".
Personally I hate it when people say "google the answer".
Web Designer / Developer. Currently working on Paphos Life.
Living in Polemi, Cyprus with my wife and daughter.