Students on an Alternative Spring Break trip to Philadelphia two weeks ago got more than pride for doing volunteer service — they got mites.

Of the 13 students who took the trip, 11 returned home to find itchy, red bumps from scabies, a skin rash caused by microscopic mites.

One student had noticed red bumps on the third and fourth day of the trip while the students were working at Hutchinson Place, a residential program for homeless, substance-addicted women and their children. The students doubted they got the condition from the center; most said they probably got it at a hostel where they stayed.

Only one student escaped the clutches of the mites altogether.

After the first student with symptoms went to a dermatologist in Philadelphia, she was treated for an allergic reaction. But more than a week after the group returned to Evanston, other members began showing the same signs of the bumps.

Health Service Director Mark Gardner said the skin condition occurs when the insects burrow into the skin and lay eggs and fecal matter. He said the mites could be under the skin for several days before skin irritation begins.

“Usually you don’t just get it and then get the symptoms right away,” Gardner said. “Sometimes it takes a very long time to develop symptoms. For some people, it might take up to a month. It’s extremely variable.”

He said the parasites only can be contagious through direct contact — unlike fleas, which are more than 10 times larger and can jump from person to person.

Weinberg senior Jenny Wu said that after the rash spread to her arms, legs, back and neck, she used a lotion to treat it. But even three weeks after the trip, the effects of the unwelcome pests have continued.

“They’ve not disappeared, but the itching has stopped,” Wu said. “The lotion kills them but it doesn’t necessarily get rid of the bumps.”

Wu said she thought the chain reaction might have begun when one person started the trip with the insects already in tow. But most of the students thought the insects could have hopped onto them from blankets they used at the hostel.

When Lisa Bayer started showing the same signs, her dad, who is a doctor, told her the rash was probably scabies.

“I thought it was from the kids, but apparently none of them has ever had scabies,” said Bayer, a Weinberg sophomore.

Gardner said the rash can be diagnosed by scraping the burrows under the skin with a scalpel and analyzing them under a microscope. But he said the most common way to know if a patient has scabies is just by talking with them to find out what they were doing during the weeks before getting the rash.

Weinberg freshman Shivani Patel said she visited the Searle Health Center three times before getting the treatment cream. First she was treated for a skin irritation and only on the second visit did the doctor diagnose it as scabies.

After using the cream and washing all her sheets and clothes, Patel said the itching has stopped, but the bumps have remained.