Try mayonnaise, like the Europeans. Put curry powder or tomato powder in it. Put little bowlfuls in an array and let him taste them. He might catch onto a different taste sensation.

Good idea, sg, but his mom has already tried mayo and he didn't like it. On the other side of the family, my niece and nephew much prefer mayo with their fries!

I'm trying to find a way to make ketchup tolerable for him.

Asian dipping sauces? I know it might be a stretch, but maybe a peanut sauce (if he has no problems with peanuts, of course), or a teryaki sauce? This depends on how adventurous the family concerned already is at the dinner table.

Mix in with some ketchup....

Make your own catsup.....and cut waaaaay down on the vinegar. It's not so much the tomato in the catsup that bothers him but the vinegar....and very lkikely all the fat in the fries, chicken strips etc that he puts it on.

1/4 cup each of chopped carrot, red beet, sweet potato, fresh cranberry. *cranberry might be a sensitivity so maybe try without first. (i buy a couple extra bags during the holidays and freeze), frozen cherries are an alternative.

1/2 cup chopped apple or pear

1/4 cup raisins

tsp cinnamon

Cover just barely with water and simmer on low heat in small sauce pan.

Let cool then blender or stick blend.

*might need to toy with amounts as the sugar is what is so appealing to kids.

A tbsp or two mayo or greek yogurt stirred in once cool gives some creaminess.

I make my own sauces and use a variation of above depending what i have on hand. I make mine spicy and use worcestershire and some soy, lemon etc and a few frozen cherry toms, sometimes rhubarb in my bbq sauce, etc. (no gut sensitivities here with tomatoes). .

Lots of variations using the basic sauce recipe above. Dates, cloves, turmeric, etc. Apple sauce in place of fresh.

Double the sweet potato and beet and it makes a good spaghetti sauce with ground chuck.

I try and stock those little packets of ketchup and mayo and fake sugars for company and kids from co-workers take-out/delivery lunches....ran out and had kid house guests once and it worked. I was making adult sauces anyway so made a kid version with what i had.

*keep an eye on it the first try as all stovetop burners vary on a simmer.

What kind of dressing does he use on salads? Rather than mayo alone, try a fry sauce - ketchup/mayo mix or a bbq sauce/mayo mix, seasoned as desired and perhaps a shot of hot sauce if he's into it but I doubt he is by the sound of things. Sounds like it's more an issue of volume of ketchup than ketchup itself being totally problematic? What about spaghetti sauce or pizza sauce? Tomatoey flavor without the vinegar volume, probably a lot less salt and sugar too so it'd be healthier too. I'd guess he would like that, it would also be simple but the issue is his tolerance to it. Contadina has a pizza sauce in a squeeze bottle so it'd be a similar look to a ketchup bottle which could also be comforting to him.

Cynic, I seriously doubt he eats salads. He comes from a family that eats lots of beef roast and potatoes, some chicken, lots of fast foods, no fish, and, as best I can tell, no ethnic foods including Mexican or Italian - and I can guarantee no Asian. I may give the pizza sauce a shot.

Sleeven, because I have all of the ingredients in your sauce, I may give it a go, but I have serious doubts it will appeal to his immature palate.

I just noticed that I referred to the little fella as my nephew. He is actually my great-nephew. I am only around him a couple of times a year and I have no influence to get him to try something new.

Has anyone ever changed the pH of ketchup by adding baking soda or any other substance?

Pasta sauce is much better with French fries than ketchup, but then I don't like ketchup and never ate it as a child either. I've not added baking soda to ketchup, since I don't have any ketchup, but if you do, the baking soda will react with the acid, neutralizing it into a salt, and therefore the ketchup will taste a bit more salty, and so you will want to cut back on the salt added to the potatoes.

I mix Habanero sauce with mayo, and that could be used as a substitute also. Start with micro amounts of hot sauce, but make sure it is one with good flavor. I grill my Habanero chilies over mesquite before making my Habanero sauce, and just a few drops of this sauce will give a very good flavor to mayo. I ate hot sauce from age six because it was prevalent in our elementary school lunchroom in central Texas.

Asian sweet chili sauce? Or, be like a Canadian and have gravy over fries. Either cream gravy made w/ an alternative milk (almond, etc.) or brown gravy. Or ranch dressing made with almond milk?

I eat mustard with fries but mustard is quite acidic. OTOH, a little mustard goes a long way.

DSII was eating jalapenos (the hot ones, not the mealy-mouth versions) on nachos from the age of about 2 1/2 so I wouldn't automatically discount Lars' hot sauce suggestion.

I agree--I think that most of the acid is in the vinegar. I'm concerned about the texture. Another possible experiment would be to try mixing the ketchup with concentrated tomato paste or sweet pepper sauce.

BUT, perhaps an even better strategy would be to introduce him to tastier dishes that don't require sauce?

I understand the dilemma. I have many food issues, but here's an alternative-- google NOMATO Sauce. It's made from beets, carrots and other things. It's a good sub for tomato sauce.

On the other hand, my older grandson (12y.o.) and daughter both dip their fries in Russian or thousand island dressing. It's mayo based with a little ketchup or chili sauce.

I don't dip my French fries in anything (I may be alone here), but if I did, it would be a béchamel or velouté sauce.

Thanks to all of you. I agree that there are many tasty alternatives. Unfortunately, this is not a family of adventuresome eaters.

I don't dip my French fries in anything

I love Spike Veg-It on home made French fries. Good home made fries don't really need anything else.

https://www.amazon.com/Spike-Vegit-Seasoning-Purpose-Sodium/dp/B0169T7UZI

I HAVE MYSELF EXPERIMENTED WITH BAKING SODA ...I JUST MAKE MY FIRST VERY OWN PIZZA "WITH" PIZZA SAUCE...I USED THE BAKING SODA TO TAKE THE ACID OUT OF THE SAUCE AND ILL BE DANGED IT WORKS.......I HAVE SEVERE GERD (ACID REFLUX) AND I CANT EAT HALF THE STUFF I LOVE......MY NEXT EXPERIMENT IS WITH TA DAAAAAAAA KETCHUP.......IF THE PIZZA SAUCE CAN BE CALMED DOWN...I THINK THE KETCHUP CAN....I DONT EAT IT OFTEN BUT I DO LOVE IT ON MY FRIES AND WITH CORN DOGS (I EAT THE CHICKEN KIND IT WORKS) SO YEAH GIVE IT A TRY JUST BE CAREFUL USE A 1/4 TSP AT A TIME...IT WILL BUBBLE ......WHEN YOU CAN PUT A PINCH IN IT AND IT "NOT" BUBBLE YOU HAVE TAKEN MOST OF THE ACIDITY OUT BUTTTTTT NOW REMEMBER IT WILL CHANGE THE TASTE SOME.......IT MAKES IT SWEETER MORE THAN TART......BUT THERE YA GO MY EXPERIENCE WITH BAKING SODA AND TOMATOE ( I EVEN FOUND A WAY TO GROW TOMATOES THAT ARE LESS IN ACIDITY YOU CAN GROW THEM AND PUT BAKING SODA AT THE BASE OF THE PLANT AND IT MAKES THEM A SWEETER TOMATO AND GUESS WHAT "LESS ACIDIC" HAVE FUN EXPERIMENT :)