The Types of Thermometers

More often than not, you can use most thermometers for the same purposes. The question is segregating them strictly for each use, for the same reasons as rectal thermometers are never used interchangeably with oral thermometers. The same concept applies when you are dealing with candy and meat thermometers. They can provide the same purposes and they often have similar range, but they should never be used cross-purpose for risk of contaminating your food.
Nobody wants potentially undercooked meat juice in their candy and nobody wants candy remains in their savory meats. Even if you wash off the thermometers, the risk of contamination and the effects of meat contamination are severe enough that it is not worth taking the risk. With that note, candy and meat thermometers have a considerable amount of overlap, but there are some other reasons to keep each thermometer assigned to the food it was made for.
The Limitations of Meat Thermometers

The real issue comes from trying to use meat thermometers for foods other than meat, specifically candy. Of course, there is the above concern of cross-contamination, but even if you are using a brand-new meat thermometer, there are other issues. The biggest issue comes from the fact that a meat thermometer’s temperature range is relatively small compared to a candy thermometer.
Typically, meat thermometers do not exceed 220 to 250 degrees Fahrenheit, since if the meat is anywhere above that temperature, it is probably burned. Candy thermometers, on the other hand, regularly exceed 350 and sometimes even 400 degrees Fahrenheit, as some candies need to reach this temperature in order to be made properly.
Using a meat thermometer will essentially only tell you that your candy has reached 220 degrees. If you need your candy to reach 350 degrees, you won’t know if it has reached that point or not. This is where the main problem of using meat thermometers with candy lies, as it simply does not encompass a large enough range of temperature.
Using Meat Thermometers for Candy
With this being said, if you know that your candy is not going to exceed a temperature of 220 degrees Fahrenheit but it needs to be above a temperature such as 100 degrees Fahrenheit, then using a meat thermometer can work out well. As long as the temperature you need to measure falls within the meat thermometer’s limited range, it can work out just fine, assuming that you have not used the thermometer on meat before.
Another thing to note is that once you use the thermometer for candy, it should stay used for candy. This may mean you have to purchase a new thermometer, but this is a mild concern compared to the risk of not being able to measure temperatures properly.
Also, meat thermometers are often much shorter than candy thermometers. This is because there is not as much of a danger of boiling, bubbling candy scalding you when you are checking the temperature of a turkey dinner. Even assuming that you can use your meat thermometer for the candy you are making, you run the risk of the thermometer being too close to the heat of the candy to safely hold in place.
Because meat thermometers can often be smaller than candy thermometers, you may not be able to safely hold it without gloves, but the gloves may be too big to read the temperature of the thermometer with. This is another obstacle that you will need to be well aware of when trying to use meat thermometers for candy
What About Using Candy Thermometers for Meat?
The main concern with switching your candy thermometer to be used for meat is that it may not be accurate enough. Because candy thermometers are designed with such a large range in mind, the range between where meat is unsafe and when it is adequately cooked can be so comparatively small that you may not be able to see the fine enough details on the candy thermometer to safely guess. This is really only a problem for thermometers with a more general range that measures the stages of candy cooking rather than showing an exact temperature, but it is something to note.
Similarly, you cannot go back to using the candy thermometer for candy if it has been used for meat. The risk of transferring harmful bacteria is too high even if you wash off the thermometer. This is only a small problem as you can simply purchase a new thermometer, but it is a problem to be aware of.
For more candy tips check out these articles