What are the side effects of antifungals?

October 9, 2025 •

4 min read

Each year in the United States, fungal diseases are linked to about 13 million outpatient visits and an estimated 7,300 deaths [1.5.1]. While effective, it's important to understand questions like, what are the side effects of antifungals?, as they can range from mild to severe [1.4.6].

Quick Summary

Antifungal medications can cause various side effects depending on the drug type and administration route. Common issues include GI upset and skin irritation, while serious risks involve liver and kidney damage.

Key Points

Route Matters: Topical antifungals cause localized side effects like itching, while oral and IV drugs can cause systemic issues like nausea and headache [1.3.6, 1.2.3].
Common Effects: The most frequent side effects of systemic antifungals are gastrointestinal, including nausea, vomiting, and diarrhea [1.2.1].
Serious Risks: Rare but serious side effects include liver damage (especially with azoles), kidney damage (with Amphotericin B), and severe skin reactions [1.4.1, 1.4.3].
Drug Interactions: Azole antifungals can interact with many other medications, such as blood thinners and statins, by affecting their metabolism [1.7.1].
Monitor and Report: Patients should monitor for signs of serious reactions like jaundice or severe rashes and report them to a doctor immediately [1.4.6, 1.6.5].
Long-Term Use: Treatment can last for months or years, which may increase the potential for side effects [1.4.1].
Class-Specific Effects: Different classes have unique risks; for example, itraconazole has been linked to heart failure-like symptoms and terbinafine to loss of taste [1.2.2, 1.2.4].

Understanding Antifungal Medications

Antifungal drugs are essential for treating a wide range of fungal infections, from common topical issues like athlete's foot to life-threatening systemic infections [1.5.2]. Because fungal cells are structurally similar to human cells, some medications can cause side effects by inadvertently affecting the patient's own cells [1.4.1]. The duration of treatment can be long, sometimes lasting for months or even years for severe infections, which can increase the likelihood of experiencing adverse effects [1.2.1].

Common Side Effects

Many antifungal medications share a profile of common, generally mild side effects that resolve on their own [1.4.6]. These are most frequently associated with oral or intravenous (IV) antifungals but can occur with any type. Common side effects include:

Gastrointestinal issues like nausea, vomiting, abdominal pain, and diarrhea [1.2.3].
Headaches [1.2.1].
Skin rashes and itching [1.4.6].

Side Effects by Administration Route

Topical Antifungals: These are applied directly to the skin or mucous membranes. Side effects are typically localized to the application area [1.3.6]. They are considered to have a lower risk of systemic side effects because of limited absorption into the bloodstream [1.3.6]. Common reactions include:

Itching, burning, or stinging [1.2.6].
Redness and skin irritation [1.2.6].
Dry or peeling skin [1.2.6].

Oral Antifungals: Taken by mouth, these drugs are absorbed systemically to treat more widespread or stubborn infections. This systemic action increases the potential for side effects beyond the localized reactions of topicals [1.3.1]. In addition to the common GI issues and headaches, oral antifungals can sometimes lead to more concerning problems. For instance, terbinafine is associated with a potential loss of taste or smell [1.2.4, 1.6.5].

Intravenous (IV) Antifungals: Administered directly into a vein, IV antifungals are reserved for serious, often life-threatening systemic fungal infections. These are the most powerful antifungals and carry the highest risk of severe side effects [1.8.2]. For example, Amphotericin B is known for causing infusion-related reactions like fever and chills, as well as potential kidney damage [1.4.1, 1.4.5].

Comparison of Major Antifungal Classes

Different classes of antifungal drugs work in different ways and have distinct side effect profiles [1.8.2].


Antifungal Class	Examples	Common Side Effects	Serious/Rare Side Effects
Azoles	Fluconazole, Itraconazole, Voriconazole	Nausea, headache, abdominal pain, rash [1.2.2].	Liver damage (hepatotoxicity), heart failure symptoms (itraconazole), vision changes (voriconazole) [1.2.2, 1.4.3, 1.4.4].
Polyenes	Amphotericin B, Nystatin	Fever, chills, muscle pain, nausea (Amphotericin B); Mild skin irritation (Nystatin) [1.4.5].	Kidney damage (nephrotoxicity), electrolyte imbalances (hypokalemia), arrhythmias [1.2.4, 1.4.1].
Echinocandins	Caspofungin, Micafungin, Anidulafungin	Headache, fever, phlebitis (vein inflammation), nausea [1.2.2].	Liver enzyme elevation, hypotension, infusion-related reactions [1.2.2].
Allylamines	Terbinafine	Headache, GI upset, rash [1.2.2].	Liver injury, changes in taste or smell, worsening of lupus [1.2.4, 1.6.5].

Serious Side Effects and Long-Term Risks

A small number of patients may experience severe adverse reactions to antifungal treatment [1.4.3]. It is crucial to be aware of these risks and seek medical attention if they occur.

Liver Damage (Hepatotoxicity): This is one of the most significant concerns with systemic antifungal use, particularly with azoles and terbinafine [1.4.1, 1.9.4]. Symptoms include jaundice (yellowing of the skin or eyes), dark urine, pale stools, loss of appetite, and persistent nausea or vomiting [1.4.6, 1.6.5].
Kidney Damage (Nephrotoxicity): Amphotericin B is particularly known for its potential to harm the kidneys [1.4.1]. Healthcare providers often monitor kidney function with blood tests during treatment.
Severe Skin Reactions: Rarely, antifungals like fluconazole can trigger severe skin reactions such as Stevens-Johnson syndrome or toxic epidermal necrolysis, which involve blistering and peeling of the skin [1.2.4, 1.4.3].
Drug Interactions: Azole antifungals, in particular, inhibit human cytochrome P-450 enzymes, which are responsible for metabolizing many other drugs [1.7.1]. This can lead to dangerous interactions with medications like certain statins, blood thinners (e.g., warfarin), and psychiatric drugs [1.7.1, 1.7.3]. Always inform your doctor of all medications and supplements you are taking.

Managing Side Effects

For mild side effects like an upset stomach, taking the medication with food may help [1.6.2]. For headaches, resting and staying hydrated is recommended [1.6.2]. It is vital to take the full prescribed course of medication, even if you feel better, to ensure the infection is fully eradicated and to prevent resistance [1.6.1]. If side effects are severe or persistent, contact a healthcare provider immediately [1.6.3]. Do not stop taking the medication without medical advice. For topical treatments, avoid products that combine an antifungal with a corticosteroid unless specifically directed, as the steroid can sometimes worsen the infection [1.6.4].

Conclusion

Antifungal medications are powerful tools in the fight against fungal infections, but they are not without risks. Side effects can vary widely, from minor localized irritation with topical creams to significant systemic issues like liver and kidney damage with oral and IV drugs [1.3.6, 1.4.1]. Patient awareness of potential side effects, diligent monitoring by healthcare providers, and open communication are key to using these essential medicines safely and effectively.

For more information from an authoritative source, you can visit the CDC's page on Antifungal Treatment.

Frequently Asked Questions

Generally, no. Topical antifungals primarily cause localized skin irritation like burning or itching. Serious systemic side effects are rare because absorption into the bloodstream is limited [1.3.6].

Signs of liver damage include yellowing of the skin or eyes (jaundice), dark urine, pale stools, loss of appetite, nausea, vomiting, and unusual tiredness [1.4.6, 1.6.5].

For headaches, the NHS advises not to drink too much alcohol [1.6.2]. Given that many oral antifungals carry a risk of liver toxicity, it is generally wise to avoid or limit alcohol. Always consult your doctor or pharmacist for advice specific to your medication.

Mild side effects are usually temporary and may not last long [1.4.6]. If side effects persist or are severe, you should contact your healthcare provider.

No. Side effects vary significantly depending on the specific drug, its class (e.g., azole, polyene), the dosage, and whether it's topical, oral, or IV [1.2.5, 1.2.2].

You should call a doctor immediately if you experience signs of a severe allergic reaction (swelling, difficulty breathing), a severe skin reaction (blistering, peeling), or signs of liver damage like jaundice [1.6.3, 1.6.5].

Yes, especially oral azole antifungals. They can interfere with the metabolism of many drugs, including blood thinners, statins, and some heart medications. It is crucial to tell your doctor about all medicines you take [1.7.1, 1.7.3].