As of 2011, NPIC stopped creating technical pesticide fact sheets. The old collection of technical fact sheets will remain available in this archive, but they may contain out-of-date material. NPIC no longer has the capacity to consistently update them. To visit our general fact sheets, click here. For up-to-date technical fact sheets, please visit the Environmental Protection Agency’s webpage.
Laboratory Testing: Before pesticides are registered by
the U.S. EPA, they must undergo laboratory testing for
short-term (acute) and long-term (chronic) health effects.
Laboratory animals are purposely given high enough doses
to cause toxic effects. These tests help scientists judge how
these chemicals might affect humans, domestic animals,
and wildlife in cases of overexposure.
- Capsaicin is an animal repellent that has also been registered
for use as an insecticide, miticide, rodenticide, and feeding
depressant.1 The International Union of Pure and Applied
Chemistry (IUPAC) chemical name is 8-methyl-n-vanillyl-
6-nonenamide and the Chemical Abstracts Service (CAS)
registry number is 404-86-4.2 Capsaicin is a phenylpropanoid
- Capsaicin is obtained from peppers which are the fruit from plants in the genus Capsicum. The peppers are ground
into a fine powder. This may be further refined to the oleoresin, which is a reddish-brown liquid with little odor.2 When
extracted from plants, the capsicum oleoresin may contain many volatile compounds in addition to capsaicin.4 Capsicum
annum fruits contained 1.27% capsaicinoids, and 0.03% capsaicin.5
- Capsaicin was first registered for use in the United States in 1962.2 It is classified as a biochemical pesticide due to its
mode of action and the fact that it is a naturally occurring substance.2 See the text box on Laboratory Testing.
Molecular Structure - Capsaicin
Physical / Chemical Properties:
- Vapor pressure6: Very low
- Octanol-Water Partition Coefficient (Kow)7: 3.04
- Henry's constant7: 1 x 10-13 atm·m3/mol at 25 °C
- Molecular weight7: 305.462 g/mol
- Solubility (water)7: 10.3 mg/L at 25 °C
- Soil Sorption Coefficient (Koc)7: 1.10 x 103
- Capsaicin is used on vegetation such as crops and trees, buildings, and garbage containers. It is registered to repel
vertebrate pests such as rabbits, squirrels, deer, voles, raccoons, cats, dogs, and skunks. It is also used as an attack deterrent
for dogs and bears.1 Uses for individual products containing capsaicin vary widely. Always read and follow the label when
applying pesticide products.
- It is applied to foliage of plants to deter feeding by insects such as spider mites, lace bugs, and other invertebrates.1
Capsaicin is used as an insecticide in addition to its use as a repellent.8
- Capsaicin is toxic to some bacteria and has been evaluated for use as a marine antifoulant.9
- Signal words for products containing capsaicin may range from Caution to Danger. The signal word reflects the combined
toxicity of the active ingredient and other ingredients in the product. See the pesticide label on the product and refer to
the NPIC fact sheets on Signal Words and Inert or "Other" Ingredients.
- To find a list of products containing capsaicin which are registered in your state, visit the website
http://npic.orst.edu/reg/state_agencies.html and search by "active ingredient."
- In addition to its use as a pesticide, capsaicin is used in law enforcement and as an ingredient in cosmetics.10 Medical
researchers have studied capsaicin and its interaction with the TRVP1 receptor for use in pain management.11,12 Capsaicin
also has been evaluated for treatment of some cancers.14
- Inhalation results in inflammation of pulmonary tissue and damage to respiratory cells.15 Capsaicin also irritates skin,
- In insects, capsaicin's toxicity appears to be through metabolic disruption, membrane damage, and nervous system
dysfunction.8 Capsaicin has also been shown to repel insects as well as kill them.18
- Capsaicin triggers the release of the neuropeptide P from the sensory nerve fibers of the C type.3 In mammals, capsaicin
binds to the TRPV1 vanilloid receptor.15 The TRPV1 receptor then releases sensory neuropeptides that trigger a
neurogenic inflammatory response.13,19
- Modes of toxicity for non-target organisms are expected to be similar to those of targeted insects and mammals.
Capsaicin is considered toxic to honeybees and other beneficial insects.8 Although birds have the TRPV1 receptor, it is not
activated by capsaicin.20,21 No information was available regarding toxicity of capsaicin to fish or other aquatic life.2
- Acute oral LD50 values were determined to be 97.4 mg/kg and 118.8 mg/kg in female and male mice, respectively, and
148.1 mg/kg and 161.2 mg/kg in female and male rats, respectively.22 See the text boxes on Toxicity Classification and
|TOXICITY CLASSIFICATION - CAPSAICIN
||Very Low Toxicity
|Acute Oral LD50
||Up to and including 50 mg/kg
(≤ 50 mg/kg)
|Greater than 50 through 500 mg/kg
|Greater than 500 through 5000 mg/kg
|Greater than 5000 mg/kg
||Up to and including 0.05 mg/L
|Greater than 0.05 through 0.5 mg/L
|Greater than 0.5 through 2.0 mg/L
|Greater than 2.0 mg/L
||Up to and including 200 mg/kg
|Greater than 200 through 2000 mg/kg
|Greater than 2000 through 5000 mg/kg
|Greater than 5000 mg/kg
|Primary Eye Irritation
||Corrosive (irreversible destruction of
ocular tissue) or corneal involvement or
irritation persisting for more than 21 days
||Corneal involvement or other
eye irritation clearing in 8 -21 days
||Corneal involvement or other
eye irritation clearing in 7
days or less
||Minimal effects clearing in less than 24 hours
|Primary Skin Irritation
||Corrosive (tissue destruction into the
dermis and/or scarring)
||Severe irritation at 72 hours
(severe erythema or edema)
||Moderate irritation at 72
hours (moderate erythema)
||Mild or slight irritation at
72 hours (no irritation or
|The highlighted boxes reflect the values in the "Acute Toxicity" section of this fact sheet. Modeled after the U.S. Environmental Protection Agency, Office of Pesticide Programs, Label Review Manual, Chapter 7: Precautionary Labeling. http://www.epa.gov/oppfead1/labeling/lrm/chap-07.pdf
- Additional LD50 values for male mice were 60-75 and 190 mg/kg depending on the carrier solution when the capsaicin
was administered within the stomach.23
LD50/LC50: A common measure of acute toxicity is the lethal
dose (LD50) or lethal concentration (LC50) that causes death
(resulting from a single or limited exposure) in 50 percent
of the treated animals. LD50 is generally expressed as the
dose in milligrams (mg) of chemical per kilogram (kg) of
body weight. LC50 is often expressed as mg of chemical
per volume (e.g., liter (L)) of medium (i.e., air or water) the
organism is exposed to. Chemicals are considered highly
toxic when the LD50/LC50 is small and practically non-toxic
when the value is large. However, the LD50/LC50 does not
reflect any effects from long-term exposure (i.e., cancer,
birth defects or reproductive toxicity) that may occur at
levels below those that cause death.
- Studies using mice have reported LD50 values ranging from 47.2
mg/kg25 to 2500.0 mg/kg.24
- The LD50 in humans has been estimated at 0.5-5.0 g/kg.25
- Capsaicin can cause skin irritation.10,16 Little absorption occurs
across the skin.12 Edema following dermal exposure in mouse
ears in several studies peaked within 1 hour of application,
although subsequent applications produced less of a
- Capsaicin can severely irritate the eyes, and was found to cause
corneal lesions in rats and mice.8,10
- The dermal LD50 was determined to be >512 mg/kg in mice, however no signs of toxicity were noted at the doses
- No inhalation LC50 was found.
- Capsaicin temporarily causes bronchoconstriction, coughing, nausea, and incoordination in the upper body in humans
- Airway resistance increased following inhalation of capsaicin in both mild asthmatics and non-asthmatic people at doses
that are below those eliciting the cough response.27
- People suffering from asthma and other respiratory diseases may be more sensitive to capsaicin than other individuals.26
- A more recent study suggested that people with sensory hyperreactivity have enhanced sensitivity to capsaicin. This was
associated with increased levels of serum nerve growth factors in nasal lavage fluid.28
Signs of Toxicity - Animals
- Capsaicin produces its repellent effect when it contacts either eye or respiratory tract mucus membranes. Signs of acute
exposure include coughing, inability to vocalize, and temporary blindness.29
- Mice and rats dosed orally with 96 to 200 mg/kg capsaicin demonstrated immediate salivation, convulsions, reddening
of the skin, and dypsnea, or labored breathing. Animals either died within 26 minutes of dosing, or showed no further
symptoms 24 hours after dosing.22
- Inhalation exposure to capsaicinoids in pepper sprays damaged rat bronchial, tracheal, nasal, and alveolar cells, causing
Signs of Toxicity - Humans
- Exposure to capsaicin pepper spray results in temporary blindness, lacrimation (tear production), burning sensation, pain
and redness on the skin, nasal irritation, coughing, bronchoconstriction, and dyspnea.26
- Capsaicin administered in a nasal spray resulted in human volunteers experiencing greatly increased nasal discharge and
lacrimation, and burning sensation.30
- Mucous membranes throughout the gastrointestinal tract from mouth to anus may be temporarily irritated by ingestion
of capsaicin. In addition to irritation, diarrhea and vomiting may occur.31
- Always follow label instructions and take steps to minimize exposure. If any exposure occurs, be sure to follow the First Aid
instructions on the product label carefully. For additional treatment advice, contact the Poison Control Center at 1-800-
222-1222. If you wish to discuss an incident with the National Pesticide Information Center, please call 1-800-858-7378.
- Chronic feeding studies in rodents consistently demonstrated weight loss when animals were either dosed via gavage or
when the capsaicin was mixed with the food.10 However, another feeding study showed no such effects using ground red
pepper Capsicum annuum at up to 10% of the total diet in mice.36
- Different diets affected the toxic effects of capsaicin on the liver and spleen in rabbits, such that effects were greatest in
animals fed the high-fat diets. In contrast, animals fed high protein, high carbohydrate diets showed no effects relative to
controls. Test animals were given 5 g/kg of "red pepper" daily for one year.32
- Researchers applied pure capsaicin topically to the backs of mice once weekly for 26 weeks. Doses of 0.64, 1.28, and 2.56
mg/mouse/week resulted in skin abnormalities including inflammation, epidermal crusts, epidermis thickening, and
ulcerations.33 Other signs included gross lesions in the stomach, salivary glands, and oral cavity.33
- Capsaicin applied to the hind paws of rats twice daily for 10 weeks led to increased pain sensitivity in the animals
exposed to the highest dose (0.75% capsaicin) although this sensitivity decreased with time.34 Rats treated with a lower
dose (0.075% capsaicin) demonstrated reduced function in certain cells known as C fibers following prolonged dosing,
but this impairment disappeared after treatment stopped.34
- No information was found regarding NOEL, LOEL, PAD, or reference dose (RfD) values for capsaicin. See the text box on Exposure.
Exposure: Effects of capsaicin on human health and the environment depend on how much
capsaicin is present and the length and frequency of exposure. Effects also depend on the health
of a person and/or certain environmental factors.
- Chronic exposure to capsaicin in a factory setting resulted in cough thresholds that were related to the extent of
exposure on the job.35 Workers exposed to capsaicin demonstrated a bimodal cough threshold response that was not
observed in unexposed workers, who showed a unimodal response. Some exposed workers were much more sensitive to
capsaicin than other exposed workers.35
- A condition known as "Hunan hand", which is a form of contact dermatitis, has been noted in workers handling
- No data were found regarding possible effects of capsaicin on endocrine systems.
- Several researchers reviewed evidence that capsaicin is carcinogenic in animals and found that the evidence was
- Researchers have demonstrated that capsaicin is mutagenic and genotoxic in some studies using bacterial and rodent
models36 but not in others.37,38
- Researchers applied pure trans-capsaicin to the dorsal skin of mice weekly for 26 weeks at rates of 0.64, 1.28, or 2.56 mg/
mouse/week.33 No increase of neoplastic skin lesions or other abnormal skin growth was noted over control mice.33
- A lifetime diet containing 0.03% capsaicin fed to mice led to slight increases in benign tumors of the cecum.39
- Capsaicinoids fed to male mice at 1% of the diet for 79 weeks resulted in kidney lesions in male mice.40 However, female
mice fed a diet of 0.25% capsaicinoids for 83 weeks developed fewer tumors compared with controls. Hepatocellular
neoplasms, or abnormal growths in the liver, also occurred less often in male and female mice fed greater concentrations
of capsaicinoids in their diet.40
- Neither the U.S. EPA nor the International Agency for Research on Cancer (IARC) has published a cancer rating for
capsaicin. See the text box on Cancer.
Cancer: Government agencies in the United States and abroad have
developed programs to evaluate the potential for a chemical to cause
cancer. Testing guidelines and classification systems vary. To learn
more about the meaning of various cancer classification descriptors
listed in this fact sheet, please visit the appropriate reference, or
- Capsaicin has demonstrated mutagenic effects in some research46 but not in other studies.26 Impurities in the extract
may be responsible for mutagenic effects because the studies that failed to demonstrate mutagenic effects used pure
- People consuming 90-250 mg of capsaicin per day (in the form of jalapeno peppers) had a greater risk of gastric cancer
compared with people who consumed less capsaicin (0-29.9 mg capsaicin per day).41
- Capsaicin exerted an anti-proliferative effect on human prostate cancer cells in vitro in a dose-dependent manner,
completely halting proliferation at 5 x 10-4 mol/L.14
NOAEL: No Observable Adverse Effect Level
NOEL: No Observed Effect Level
LOAEL: Lowest Observable Adverse Effect Level
LOEL: Lowest Observed Effect Level
- Offspring of pregnant rats treated with 8% wet weight capsaicin via a 50
cm2 dermal patch had delayed ossification in their metatarsal bones. This
dose was above the NOEL for the mothers.42 See the text box on NOAEL,
NOEL, LOAEL, and LOEL.
- Rabbit fetuses were unaffected at all maternal doses tested although the dams showed signs of toxicity at the higher
doses.42 The authors concluded that trans-capsaicin should not be considered a developmental toxicant.42
- A review of studies that involved injecting capsaicin into subject animals documented developmental and reproductive
effects such as reduced growth and contraception rates in some studies, but no effects in others.10
- No human data were found on the teratogenic or reproductive effects of capsaicin.
- Little absorption occurs across the skin.12
- Researchers applied 0.8 g of gel containing 0.075% of capsaicin to the skin of six human volunteers for eight hours of
exposure. They then calculated the average absorbed dose as 22.65 μg/cm2 with a standard deviation of 3.73 μg/cm2.49
- Topical application of pure capsaicin to the skin of mice resulted in peak plasma concentrations occurring 4 to 12 hours
later, and capsaicin was detectable in the blood 24 hours after dosing. Doses of 5.12 mg/mouse/week led to maximum
plasma concentrations of 51.50 ng/mL in male and 84.80 ng/mL in female mice.33
- Capsaicin fed to rats was rapidly absorbed from the stomach, with 85% of a 3 mg dose absorbed within three hours.43
- Rats injected intravenously accumulated capsaicin primarily in the brain and spinal cord three minutes after dosing, with
lower levels found in the liver and blood. Ten minutes after dosing, the greatest concentrations remained in the spinal
- When the capsaicin was injected subcutaneously, rat blood concentrations peaked five hours following dosing, and brain
and spinal cord tissue concentrations were somewhat lower. Kidneys contained the greatest concentrations and liver
concentrations were low. Researchers detected capsaicin in all tissues 10 minutes following dosing but residues were
undetectable in any tissues 17 hours later.44 The researchers concluded that the low concentrations in the liver were due
to metabolic breakdown of the capsaicin.
- Distribution data for capsaicin in humans were not found.
- Metabolism occurs primarily by the liver in the rat.45
- Metabolism of capsaicin by P450 enzymes may follow a number of pathways and produce a variety of metabolites, some
of which may be associated with increased toxicity.46
- Research using human, rat, mouse, goat, and rabbit liver and lung microsomes demonstrated that metabolism rates were
much greater in liver microsomes compared with lung microsomes for each species. Although the same metabolites
were produced, the relative amounts of each metabolite were species-dependent.47
- No metabolism data were found for humans.
- Less than 10% of an oral dose of capsaicin given to rats was excreted unchanged 48 hours after dosing.43
- No information on urinary/fecal metabolites and biomarkers was available.
- No data for human excretion were found.
- Medical tests are not generally available to detect or quantify capsaicin in the human body.
- Capsaicin should not be very mobile in soil based on its chemical properties.7
- Volatilization from either wet or dry soil is not expected based on the Henry's Law Constant and the vapor pressure,
The "half-life" is the time required for half of the
compound to break down in the environment.
1 half-life = 50% remaining
2 half-lives = 25% remaining
3 half-lives = 12% remaining
4 half-lives = 6% remaining
5 half-lives = 3% remaining
Half-lives can vary widely based on environmental
factors. The amount of chemical remaining after a
half-life will always depend on the amount of the
chemical originally applied. It should be noted that
some chemicals may degrade into compounds of
- Soil bacteria break capsaicin down into vanillylamine, which is
further broken down into vanillin, vanillyl alcohol and vanillic
- Capsaicin applied to a compacted sandy loam with 2.5% organic
matter and a pH of 7.9 did not move from the point of application
over a 9-day period, with unspecified irrigation or rainfall.49
Researchers concluded that soil compaction may have prevented
- Researchers studying persistence of capsicum oleoresin in a
sandy loam soil estimated half-lives of 2 to 8 days.50 Researchers
suspected that the capsicum oleoresin leached from the test soil
based on the color of the water collected at the base of the test
bins.50 See the text box on Half-life.
- Breakdown by photolysis or hydrolysis is not expected due to capsaicin's molecular structure and solubility.7
- Based on its Kow and Koc values, capsaicin is predicted to bind to the surface of sediments and suspended solids.7
Therefore, the potential for groundwater contamination by capsaicin is low.
- Capsaicin has a low potential for volatilization based on its vapor pressure.7
- Laboratory and field data related to capsaicin's fate in water were not available.
- Due to its low vapor pressure, capsaicin will exist only in particulate form in the atmosphere, and be subject to wet and
dry deposition processes.7
- Capsaicin's chemical structure suggests that photolysis will not be a major degradation pathway.7
- Capsaicin is an extract of the fruits of the plants in the genus Capsicum.2
- No information was found regarding the transport, distribution, or metabolism of capsaicin in plants, nor were data
available for the foliar half-life of capsaicin.
- No data were found on capsaicin's indoor persistence.
- Capsaicin has been used in human cuisine as an ingredient and as a condiment for many years.16,17,41
- Capsaicin is exempted from the requirement of a residue tolerance.51
- No toxicity information or field studies involving birds were found for capsaicin.
- Birds do not detect capsaicin. Although birds possess the TRVP1 receptor in their nerve cells, it is not activated by
capsaicin as it is in mammals.20,21
- Ecologically, capsaicinoids may function to protect the seeds within the fruit.52 They may also influence seed dispersal
patterns by influencing gut retention times of the seeds, resulting in more successful plant reproduction.53
Fish and Aquatic Life
- No studies were found evaluating the toxicity of capsaicin to aquatic life.
- In its Reregistration Eligibility Decision, the U.S. EPA waived the ecological effects studies that are typically required
because it was determined that restrictive labeling would adequately protect aquatic species.2
- Based on its chemical characteristics, a moderate potential for bioconcentration is expected for capsaicin.7
- Capsaicin is toxic to bees and other beneficial insects.8
- No other information for terrestrial invertebrates was
Reference Dose (RfD): The RfD is an estimate of the quantity of
chemical that a person could be exposed to every day for the rest
of their life with no appreciable risk of adverse health effects. The
reference dose is typically measured in milligrams (mg) of chemical
per kilogram (kg) of body weight per day.
U.S. Environmental Protection Agency, Technology Transfer Network, Air Toxics Health
Effects Glossary, 2009. http://www.epa.gov/ttnatw01/hlthef/hapglossaryrev.html#RfD
- No reference dose (RfD) exists for capsaicin. See the text box on Reference Dose (RfD).
- No cancer classification has been made for capsaicin. See the text box on Cancer.
Date Reviewed: October 2008
Please cite as: Gervais, J. A. ; Luukinen, B.; Buhl, K.; Stone, D. 2008. Capsaicin Technical Fact Sheet; National Pesticide
Information Center, Oregon State University Extension Services. http://npic.orst.edu/factsheets/archive/Capsaicintech.html.