Why’s My Diffuser Smelly? How to Diagnose and Fix the Problem

Do you love using an essential oil diffuser to freshen up your home but find that it starts to smell a little funky after a while?

A smelly essential oil diffuser is actually pretty common, but the good news is that in most cases, it’s an easy problem to diagnose and fix.

This article provides a complete troubleshooting guide to help you figure out why your diffuser smells and how to get it back to smelling sweet again!

There are a few common reasons why your essential oil diffuser may start to emit less-than-pleasant odors. The smelly culprits usually include:

  • Buildup of oil residue
  • Mold or mildew growth
  • Using too much oil
  • Old or expired oils
  • Certain oil combinations that don’t mix well

By following the step-by-step troubleshooting approach below, you can get to the bottom of what’s causing the stink and banish bad smells for good.

Troubleshooting a Smelly Diffuser Step-By-Step

When you notice your essential oil diffuser starting to smell funky, the first step is to try to identify the specific odor. This can help narrow down what’s causing it. Some common smelly diffuser odors include:

  • Burnt plastic smell
  • Fishy smell
  • Musty, moldy smell

Once you identify the type of odor, you can start troubleshooting. Here is a step-by-step guide:

1. Clean the Diffuser Thoroughly

Nine times out of ten, a thorough cleaning will eliminate a smelly essential oil diffuser. Make sure to use natural, odorless cleaning solutions that won’t leave residues. Some good options include:

  • White vinegar – Mix equal parts vinegar and water and run through diffuser. Rinse well. The acetic acid in vinegar breaks down oil buildup.
  • Rubbing alcohol – Dampen a cloth with rubbing alcohol to wipe down all diffuser surfaces. Evaporates quickly without residue.
  • Dish soap – Use a mild, unscented dish soap and warm water to wash the diffuser basin and interior. Rinse thoroughly.

Be sure to scrub corners, crevices, and any diffuser parts with a cotton swab or toothbrush. Rinse all soap away.

Why's My Diffuser Smelly? How to Diagnose and Fix the Problem

2. Establish a Regular Cleaning Schedule

To prevent future smells, stick to a regular diffuser cleaning schedule. Generally, a quick wipe-down between uses and a thorough cleaning 1-2 times per month works well.

3. Use Less Oil

If you notice a smell after using certain oils, try reducing the amount of drops you use per diffuser session. Typically 3-5 drops total in the basin is plenty. Too much oil can leave residue.

4. Switch Up Your Oils

The smell may be the result of certain essential oil combinations that don’t complement each other. If the smell persists after cleaning, try alternating different oils that have more harmonious scents.

5. Replace Old Bottles of Oil

Check expiration dates and give very old bottles of essential oil the sniff test. Oils can oxidize and go rancid over time, producing bad smells. Replace expired oils.

6. Replace the Diffuser

If foul smells persist after thorough cleanings and oil adjustments, the diffuser itself may be beyond saving. Look for signs of mold, cracks, or corroded parts. Invest in a new, high-quality diffuser.

Preventing Bad Smells in Your Diffuser

With the right care, you can avoid stinky diffuser syndrome in the future:

  • Clean regularly
  • Use proper oil amounts
  • Store oils correctly
  • Avoid offensive oil combinations

Proper cleaning is key – don’t let oil residue build up. And be mindful of how much oil you add and how long you diffuse. Oils like citrus or mint can be irritating in excess.

When to Replace Your Essential Oil Diffuser

Essential oil diffusers have a finite lifespan. Signs yours may need replacing include:

  • Persistent bad smells after cleaning
  • Visible mold, mildew or cracks
  • Weak mist output even after cleaning
  • Overheating
  • Very old age (5+ years)

High-quality diffusers can last 3-5 years with proper maintenance. Look for BPA-free plastic or durable materials like glass, ceramic or wood. Avoid “bargain” diffusers with brittle plastic parts.

A few top-rated diffuser brands are URPOWER, InnoGear, and Vitruvi.

Common Questions about Smelly Diffusers

Why do my oils smell bad in the diffuser?

If stored oils smell rancid, they may have expired or degraded. Oils can also smell bad in a diffuser if buildup wasn’t cleaned thoroughly.

Why does my diffuser smell musty?

Musty, moldy smells mean mold has grown in the stagnant water left in a diffuser that wasn’t cleaned. Always dump water after use.

Can diffusers get moldy?

Yes, diffusers can definitely get moldy if not cleaned routinely. Mold spores thrive in the damp environment. Be sure to fully dry all parts after cleaning.


While it’s frustrating when your essential oil diffuser starts emitting less-than-pleasant scents, in most cases the problem can be quickly identified and remedied. With this comprehensive troubleshooting guide, you now have the key steps to diagnose what’s causing the smell and fix it fast.

Just be diligent about regular cleanings and proper oil use. With a little diffuser TLC, you’ll be breathing easy in no time!

What tricks have you used to fix a smelly essential oil diffuser? Share your tips in the comments below!