Sex is good! Dogs are good! Sex with dogs is NOT good!

O2 is great! Vital, even! Unpaired oxygen is highly toxic to all forms of life

Alcohol is generally well tolerated in reasonable quantities, the common ink cap mushroom is edible, but if eaten alongside alcohol it becomes poisonous

Can't think of anything myself, but I just want to say this is a really good unique question.

When she says "don't" and when she says "stop".

Some might disagree but the one time I melted cheddar cheese on popcorn I nearly barfed.

Politicians and guillotines are terrible on their own, but when combined....

Chemistry is so weird like that, you should see the Nile red stuff where he turns paint thinner into cherry soda https://youtu.be/NIVkBs7oWDI?si=EK4OnaCu-zw4Ffzr

Or plastic gloves into hot sauce https://youtu.be/1B3Xi5L6siI?si=hqti_mueK2o-0A_h

Or cotton balls into cotton candy https://youtu.be/vHuFizITMdA?si=5-KRqq1qUz3S9Znq

Grapefruit fucks with a lot of medications (if you regularly eat grapefruit, check to make sure none of your medications are affected by it). The effects can range from nullifying the medication, to increasing the effects (potentially fatally), or causing the medication to become toxic (also potentially fatally).

Wrinkly, wet fingers (after a nice long shower) grabbing soft, dry, fluffy blankets. Eeeeuuuuggggghhhhjjjjj. God, it hurts just thinking about it.

Steak sause and ice cream is bad, Making out and cousin are meh on their own but great together.

I don't like espresso, or any coffee really, and I definitely don't like Liquor 43. But there's a South American cocktail called a Carajillo that's those two ingredients, fresh espresso and Liquor 43 and nothing else, dry shaken together... and its friggen delicious. Just absolutely amazing.

Fruit yoghurt is nice, soda is nice.

Mixing them is abomination.

Chlorox and ammonia are effective cleaners on their own and life threatening if mixed.

Sugar and acidity go together well but can be unpalatable on their own at the levels that theyre used. i.e 45 grams sugar / can would gag you without that acidity. the acidity on its own would not taste great.

Some spices synergize with other spices but arent great by themselves.

fat by itself: gag, bread by itself: boring, bread + fat: tasty

Carbon Dioxide is poisonous by itself but in small amounts it can stimulate breathing. Pure Oxygen can cause nerve damage over long periods of time but is necessary for survival. Nitrogen isnt poisonous but it cant support life on its own either. The three mixed together in the right proportions is breathable over the long term (air)

Penacillin type antibiotics dont work on resistant strains on their own and drugs that inhibit the enzymes that bacteria use to neutralize those antibiotics wont do anything on theur own but together, they can kill bacteria that used to be vulnerable to antibiotics but developed resistance to them.

Alloys are examples of materials that are greater than the sum of their parts.

Sulfur, charcoal and saltpeter are relatively unremarkable. Sulfur and charcoal burn but not particularly violently. Saltpeter doesnt do much unless it is paired with fuel. Together they make gunpowder.

The gases of Hydrochloric Acid and Ammonia mixed together form Ammonium chloride. Which, among other things, is used as salmiak to make salty licorice.
I remember making this in high school, it's the very first thing that pops in my head whenever I think of bad + bad = good. Granted, you must like salty licorice, or it'll be bad + bad = disgusting :)

Nuts & gum.

Tooth paste and orange juice.

Blue cheese and orange juice! It's such a bad combo it's worth trying.

Skittles and M&Ms. Trust me. They smell great but are inedible together.

Butternut squash soup is awful without any spices and spices are too strong to be ingested by themselves but together it's one of the best soups.

I'm in the minority with this. But I like bananas on their own. And I like milk on its own. But I don't like banana milk.

Tuna fish milkshake

Gummy bears + Spaghetti with meatballs

Love onions and love gravy. Put them together and we’re going fall out quickly.

You can't live without Na, it's vital for your body to function.