Q. I am the grandmother of 4-year-old fraternal twin girls, who are good most of the time, but when they are bad, they are really bad. Although one grandchild is usually sweet and good-natured, the other is prone to daily meltdowns. Something always goes wrong for this little girl, so she always has something to scream about.

I am also afraid that my daughter — a stressed and struggling single parent — is making her behavior worse. Because a timeout doesn’t seem to help this child, my daughter uses the belt. She just gives her one or two whacks on her legs, but I tell her that her child would act better if she talked to her when she was being pouty and mean to her sister, and if she ignored her meltdowns whenever she could.

I also try to reassure my daughter by telling her that her child is pushing the limits, but that her behavior is normal and that she doesn’t need an exorcist. But am I correct?

A. This child doesn’t need an exorcist, and she also doesn’t need those whacks on her legs.

(Hadley Hooper/For The Washington Post)

Your daughter might not know it, but she is taking unfair advantage of her child when she uses that belt, because she is much bigger than her daughter; because she might be hitting her harder than she thinks and because a 4-year-old is too young, too small and too scared to fight back. That might not be the case in 10 years. By then your granddaughter will be as big as her mom, and if she’s mad enough, she might give back some of the physical and emotional pain that her mother once gave to her.

There are better ways to discipline a child.

Ask your daughter to praise her child’s good behavior much more than she corrects her mistakes. She should talk with her daughter about her feelings when the child is happy and not in a funk, and have these conversations when they’re in a car or on a walk or in the dark. Even adults are more confiding when they’re not looking each other in the eye.

If this doesn’t help your granddaughter act better, she might have one of those hard-to-spot physical problems that make children’s behavior go haywire. Many doctors don’t make these connections and many dietary tests aren’t great, but your daughter can safely play detective herself.

She only has to look around the mall to see that everyone looks different; they are different on the inside, too.

Some children fall apart because they’re hypoglycemic and need to eat a little protein every few hours to keep their blood sugar steady. Others misbehave because their central nervous systems are sensitized to a food or inhalent.

Other children get depressed, headachy or hyperactive when they take an aspirin or eat an orange, an apple, a tomato or another food that contain salicylates, a chemical that’s in some plants to keep them healthy. And if a child can’t tolerate salicylates, they usually can’t tolerate dyes and preservatives, either, which are often made from petrochemicals.

And then there are the children whose behavior falls apart if they drink milk or eat ice cream or cheese because their bodies can’t process the protein or the whey — or both — that is in casein. Not every gut can handle the gluten that’s in wheat and other grains.

If your daughter decides to check out these diets, ask her to keep a food and behavior diary, so she can see whether a food or an inhalant is causing a bad reaction. She might think that this testing is too much trouble, but it’s a lot easier than dealing with this endless round of meltdowns.

To make your daughter’s detective work easier, print out information on these diets before they begin. You’ll find the best material on gluten intolerance; on casein intolerance and Pub Med; and on dyes and salicylates. If a special diet helps her child, you can then find the support group, the Web sites and the books to help her stick with it.

Send questions about parenting to advice@margueritekelly.com

Read a transcript of a recent live Q&A hosted by Kelly and read past Family Almanac columns. Her next chat is scheduled for Nov. 15.