Have you ever Noticed that One Child just Never seems to get Head Lice?

Different blood types are typically the reason that not all family members will get lice.
Different blood types are typically the reason that not all family members will get lice. Lice have a hard time spreading to a person with a different blood type than the original host.


Head lice are a human parasite that invade our hair and nourish on our blood. Although they feed on our blood, fortunately they do not spread disease. Most children get lice at least once in their lifetime, but have you ever noticed that one of your children just never seems to get it? The reason for this phenomenon has to do with variations in blood type.

There are four different blood types which are O, A, B and AB. Each blood type has either a positive or negative Rh factor; there are O-, O+, A-, A+, B-, B+, AB- and AB+. Your family can have a variety of blood types and Rh factors. It is very laborious for lice to transfer and thrive from a negative blood type person to a positive blood type person or from a positive to a negative. For example if you have one A+ child and one B- child, odds are that the B- child will not get lice since the infestation from one child will not be able to thrive on the other.

On the NCBI website they tested this phenomenon in an experiment they conducted with lice and different blood samples. In the experiment they allowed lice to feed on human blood of one blood type with a positive Rh factor followed by a different blood type with a negative Rh factor. The researchers observed that when feeding on the different blood type, the lice took significantly smaller blood meals, their longevity was reduced and afterwards the female lice laid fewer eggs. Ultimately this experiment showed that lice struggle to thrive from one Rh factor to another.

Head lice do not care about the blood type someone has, it is the Rh factor of the host that will determine if the infestation will thrive or not. Transferring from blood type to blood type does not affect their infestation but going from a negative to a positive host will play a role. Just because your child infrequently seems to get head lice does not mean they cannot get it at all. Negative Rh factor blood types are still just as susceptible as anyone else despite it being harder for them to receive it from a family member. They can still get it from head to head contact with friends at school or in the neighborhood. So even for the one “lucky” child who seems to skate by any time a sibling gets lice, make sure that you still take the necessary precautions and preventative actions.