1 What is Cruex?

Brand: Cruex, Desenex, Pedi- Pro, Protectol, Tirfungol, Undelenic

Generic: Undecylenic Acid

Brand name:

Cruex, Desenex, Pedi- Pro, Protectol, Tirfungol, Undelenic.

Undecylenic acid is an anti-fungal drug, used to treat skin infections including athlete’s foot, diaper rash, jock itch and other skin conditions that are caused by fungus. However, do not use this medication to treat nail and scalp fungal infections.


Read your medication guide and follow your doctor’s prescription at all times.

  • Apply undecylenic acid topically or on your affected skin, 2 times a day per doctor’s prescription. This drug is for externally use only; so, do not ingest it.
  • Wash hands before and after you apply this topical medication unless if the hands are part of the treatment site. Likewise, wash the affected site with water and non- irritating soap, rinse properly and pat it dry.
  • The dosage depends on your medical condition or treatment response. Do not adjust your dose without your doctor’s recommendation.
  • Do not let this topical medication from getting in contact with your eyes, mouth, nose or vagina. Otherwise, rinse these sites with water immediately.
  • Avoid covering the treated site.
  • Continue using this medication on regular schedule (same time of the day). Do not stop taking this medication abruptly without consulting your doctor.

Inform your doctor immediately if your condition aggravates or does not improve.

Apply your missed dose as soon as possible. However, make sure that the time interval between the missed and the next dose is not too close. 

Otherwise, stick with the regular schedule and leave out the missed dose. Do not double dose to cover up a missed dose. Record your missed dose and inform your doctor immediately if you missed several doses.


Undecylenic acid may interact with other skin products.

Some drugs may either lessen the beneficial effects or worsen the side effects of undecylenic acid. Likewise, undecylenic acid may make some drugs less efficient or intensify their side effects.

Make sure to inform your doctor about all other drugs you are currently taking or using (prescribed and non-prescribed medications including vitamins, minerals and herbal products) to check for possible drug interaction with undecylenic acid.

Never alter the doses of other medications while on undecylenic acid neither stop nor start any medicine without the doctor’s recommendation.

Side Effects:

There are no side effects known aside from a possible allergic reaction in people who have previous or unknown hypersensitivity to the drug.

Watch out for signs of allergic reactions such as:

  • Rash
  • Itching
  • Swelling


Before taking undecylenic acid, tell your health care provider if you have/are:

  • Any allergies to any substance, food or medication, particularly to undecylenic acid;
  • Pregnant, planning to get pregnant or currently breastfeeding a baby (It is not known if undecylenic acid can harm the unborn child or if it can pass through breast milk that may harm the nursing child. The risks and benefits of using this medication during pregnancy must be discussed well with your doctor.)