The most reliable way to sterilize a cup is to boil it in water for 5 to 7 minutes. This applies to menstrual cups, baby training cups, and most silicone or glass drinkware. The method changes slightly depending on what kind of cup you’re working with, so here’s what to do for each situation.
Boiling: The Standard Method
Boiling works because water at 212°F (100°C) kills bacteria, viruses, and fungi on contact within minutes. Medical-grade silicone, the material in most menstrual cups, can safely withstand temperatures up to 450°F, so boiling water won’t damage it.
Fill a pot with enough water to completely submerge the cup. Bring the water to a rolling boil, then place the cup in. Let it boil for 5 to 7 minutes. The most important thing during this process is staying nearby. If the water boils off, silicone touching a dry, hot pan will scorch and potentially ruin the cup. Use clean tongs to remove it, and let it air-dry on a clean dish towel or paper towel.
Sterilizing a Menstrual Cup
For menstrual cups, sterilize by boiling at the beginning and end of each menstrual cycle. You don’t need to boil it every time you empty it during your period. Between removals during a cycle, a rinse with clean water or a gentle, unscented soap is enough.
Some menstrual cup brands sell specialized washes, but plain, fragrance-free soap does the same job. What matters more is knowing what to avoid. Don’t clean a menstrual cup with antibacterial soap, scented soap, baking soda, bleach, hydrogen peroxide, rubbing alcohol, vinegar, or dish soap. These can degrade the silicone, leave residue, or disrupt vaginal pH. Oil-based soaps are also off the list because they can leave a film that breaks down silicone over time.
If you’re in a situation where boiling isn’t possible (traveling, shared kitchen, no stove access), you can place the cup in a microwave-safe container filled with water and microwave it for 3 to 5 minutes. Some companies sell microwave sterilizer cases designed for exactly this. Just make sure the cup stays fully submerged.
Cleaning the Suction Holes
Most menstrual cups have tiny holes near the rim that help create and release suction. These can trap residue. Before sterilizing, fill the cup with water, place your palm over the top, and squeeze. This forces water through the holes. You can also use a soft toothbrush or a toothpick to gently clear them.
Sterilizing Baby Cups and Feeding Items
The CDC recommends sanitizing all infant feeding items, including training cups, sippy cups, and their lids and valves, after every wash until a child’s immune system is more developed. The process starts with a full cleaning in hot, soapy water, then moves to sanitizing.
You have three options:
- Boiling: Disassemble the cup completely. Place all parts in a pot, cover with water, bring to a boil, and boil for 5 minutes. Remove with clean tongs.
- Steam: Use a microwave or plug-in steam sterilizer. Follow the manufacturer’s instructions for your specific device. This is often the most convenient option for parents sterilizing items daily.
- Bleach solution: If you can’t boil or steam, mix 2 teaspoons of unscented household bleach per gallon of water. Submerge all parts for at least 2 minutes, making sure no air bubbles are trapped. Don’t rinse afterward. The trace bleach breaks down as it dries and won’t harm your baby. This is the same sanitizing standard used in restaurant dishwashing.
After sanitizing by any method, let everything air-dry on a clean, unused towel. Don’t pat or rub items dry with a dish towel, because towels can transfer bacteria right back onto the freshly sanitized surface.
One important step: check the manufacturer’s label before boiling plastic cups. Not all plastics tolerate boiling water. Silicone and glass are always safe to boil. Hard plastics labeled BPA-free are usually fine, but softer or cheaper plastics can warp.
What About UV Sanitizers?
UV-C light sanitizers have become popular, especially compact models marketed for menstrual cups and baby items. UV-C light does kill microorganisms, but its effectiveness depends heavily on whether the light can reach every surface. Cups are deep, curved objects with folds and crevices. UV-C light travels in straight lines and can’t reliably reach shaded areas inside a cup, which means parts of the surface may not be fully sanitized.
If you use a UV sanitizer as a convenient between-uses option, that’s reasonable. But it shouldn’t replace boiling as your primary sterilization method, especially for menstrual cups or infant feeding items where thorough sanitization matters most.
Sterilizing Glass and Ceramic Cups
If you’re sterilizing a glass or ceramic drinking cup (for canning, fermentation, or after illness), boiling works the same way. Submerge the cup in water before turning on the heat. Placing a room-temperature glass into already-boiling water risks thermal shock, which can crack it. Let the water and glass heat up together, boil for 10 minutes, and then let everything cool in the pot before removing.
For standard kitchen use, your dishwasher’s sanitize cycle reaches 150°F or higher, which is enough to kill common household bacteria on drinking cups. A full sterilization by boiling is only necessary in specific situations: after someone in the house has been sick, when preparing jars for food preservation, or when a cup has been stored unused for a long time.
Storing a Sterilized Cup
How you store a cup after sterilizing matters almost as much as the sterilization itself. A menstrual cup should go into a breathable cotton pouch, not a sealed plastic bag or airtight container. Silicone needs airflow to stay dry. Trapped moisture creates the exact environment bacteria thrive in.
Baby feeding items should be stored in a clean, dry, protected area once fully air-dried. If items are put away while still damp, bacteria can begin growing again within hours. The same principle applies to any cup you’ve sterilized: let it dry completely in open air before putting it away.