Advising a client or potential client on what type of pet is best for their family can be tricky. But a new study might make the answer at least a little clearer.

The study, "Opposing Effects of Cat and Dog Ownership and Allergic Sensitization on Eczema in an Atopic Birth Cohort," followed a group of one-year-old children up until age four. The children were tested for various allergies, including dog and cat allergies.

By age four, 14 percent of the children had eczema, defined as a parental report of scratching, and redness, "raised bumps," or dry skin/scaling for 6 of the last 12 months. The study found that children who were allergic to dogs but had no dog in the house were four times more likely to develop eczema than dog-allergic children in homes with a dog.

In other words, children who were allergic to dogs were less likely to get eczema if there was a dog in the house.

However, the opposite was true for children in homes with cats. Cat-allergic children were more likely to develop eczema if there was a cat in the house.

The authors concluded: "Dog ownership significantly reduced the risk for eczema at age 4 years among dog-sensitized children, cat ownership combined with cat sensitization significantly increased the risk."