Harry, Hermione, and a Hanky

In OotP, a bowtruckle strikes at Harry's hand, taking in two deep cuts and blood pouring out of them.

"When the bell echoed distantly over the grounds, Harry rolled up his blood-stained Bowtruckle picture and marched off to Herbology with his hand wrapped in Hermione’s handkerchief, and Malfoy’s derisive laughter still ringing in his ears." OotP, Chapter 13, Detention with Dolores

It is quite clear that Hermione offers her handkerchief to Harry to suppress more blood from pouring further out the cuts. Now for the fun fact: It is a common knowledge that ribbons, scarves, and or handkerchiefs are symbols of romance. In fact, in medieval times, during the Arthurian era, a knight carries with him into battle a lady's ribbon, scarf or a handkerchief as a token of her love.

Furthermore, handkerchiefs have always been associated with weddings, a keepsake passed on (a tradition dating back to the Victorian times) as something borrowed, old, new, or blue. Handkerchiefs still hold quite the significance when tying the knot nowadays. Bottomline: Hermione offering her handkerchief to Harry = yet another subtle love symbolism by JKR. 

credit to .annie. for the idea and for pointing out that Hermione is a SCARlet woman!
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