Awaiting expert review. This page covers safety or regulatory rules that change over time. It is kept out of search results until a qualified reviewer has checked it; the sources below are dated so you can verify each point.
Quick answer
Pesticide signal words are the words DANGER, WARNING or CAUTION that federal rules require on the front of most pesticide labels, chosen by the product’s most severe acute toxicity result, to show at a glance how harmful short-term exposure can be.
DANGER is the highest level and CAUTION the lowest. Products in the lowest category for every exposure route need no signal word at all. None of the words means a product is safe.
Quick facts
The key facts about Pesticide Signal Words, with sources:
- Rule
- 40 CFR 156.64 1
- DANGER
- Toxicity Category I; “Poison” and skull and crossbones if Category I by mouth, skin or breathing 12
- WARNING
- Toxicity Category II 1
- How it is chosen
- The most severe result of five acute toxicity studies 2
- Placement
- Front panel, near “Keep Out of Reach of Children” 2
- One word only
- A label may not show different signal words in different places 1
Key takeaways
- The signal word tells you how acutely toxic a pesticide is: DANGER is highest, then WARNING, then CAUTION.
- It is set by the worst result across five short-term tests: swallowing, skin contact, breathing, eye and skin irritation.
- DANGER products that are highly toxic by mouth, skin or breathing also carry “POISON” in red and a skull and crossbones.
- CAUTION means lower acute toxicity, not no hazard; the label still binds.
- The signal word on a safety data sheet may differ, because OSHA uses a different system.
What a signal word tells you
A signal word is a one-word warning printed on the front of a pesticide. The EPA’s Citizen’s Guide puts it simply: the signal word tells you how poisonous the product is to humans 7.
Technically, it reports acute toxicity: harm from a single or short exposure. The EPA assigns each product a toxicity category from I (highest) to IV (lowest) for each of five tests. The signal word follows the most severe category from any of them 2.
NPIC adds that the word reflects the most sensitive route of exposure, not an average 5. A product that is mild if swallowed but corrosive to eyes still gets DANGER.
The signal word is one part of the pesticide label. It works with the precautionary statements and first aid sections, which explain what the hazard is and what to do.
How the signal word is chosen
- Five tests are run. Acute oral, acute dermal (skin), acute inhalation, primary eye irritation and primary skin irritation 2.
- Each test gets a category. I, II, III or IV, using EPA cut-offs 5.
- The worst category wins. The signal word follows the most severe category across all five 2.
- Special ingredients can raise it. EPA recommends DANGER for formulations with 4% or more methanol, regardless of test results 2.
- Poison symbol is added if needed. Category I by mouth, skin or breathing adds “POISON” in red and the skull and crossbones 12.
- It goes on the front panel. Near “Keep Out of Reach of Children,” in capital letters, and again with the hazards-to-humans heading 2.
- Five acute studiesOral, dermal, inhalation, eye, skin
- Category per studyI, II, III or IV
- Most severe categoryThe one that decides
- Signal wordDANGER, WARNING, CAUTION or none
- Front panelGrouped with child hazard warning
The signal words and their toxicity categories
| Signal word | Category | Oral LD50 (mg/kg) | Eye effects |
|---|---|---|---|
| DANGER (may add POISON) | I – high | 50 or less 5 | Corrosive, or irritation lasting over 21 days 5 |
| WARNING | II – moderate | Over 50 to 500 5 | Irritation clearing in 8–21 days 5 |
| CAUTION | III – low | Over 500 to 5,000 5 | Irritation clearing in 7 days or less 5 |
| None required (CAUTION optional) | IV – very low | Over 5,000 5 | Minimal effects clearing in under 24 hours 5 |
NPIC’s fact sheet was last reviewed in 2008 and notes it may not be fully current; the category system itself is set in EPA regulations 51.
Example: five products, five sets of test results
These are the EPA’s own teaching examples from its Label Review Manual (Chapter 7, Table 2). They show that one bad result decides the word.
| Product | Test categories (oral / dermal / inhalation / eye / skin) | Correct signal word |
|---|---|---|
| A | III / IV / III / III / IV 2 | CAUTION |
| B | IV / III / IV / II / IV 2 | WARNING: eye irritation sets it |
| C | I / III / III / I / II 2 | DANGER and POISON: Category I by mouth |
| D | III / IV / III / I / IV 2 | DANGER: eye result only, so no POISON |
| E | III / III / III / III / III, plus 4%+ methanol 2 | DANGER and POISON: methanol rule |
Product D is the one to remember. It is only mildly toxic if swallowed but gets DANGER because it can badly damage eyes. The POISON symbol is reserved for Category I by mouth, skin or breathing 2.
Where you will see signal words
On the front panel of almost every pesticide, on its own line close to “Keep Out of Reach of Children.” The EPA prefers the child warning above the signal word 2.
Again on the back, at the head of the “Hazards to Humans and Domestic Animals” section, followed by statements such as “Harmful if swallowed” 2.
On a safety data sheet, in section 2. That word follows OSHA’s GHS rules and may not match the label 3.
In conversation with a pest company. Ask what signal word is on each product they plan to use, especially indoors or around pets. Our pesticide safety guide covers the other questions.
What signal words do well, and where they stop
Useful for
Limits of the signal word
One word cannot carry every hazard. A CAUTION product can still be very toxic to fish or bees; that shows up in the environmental hazards section, not the signal word 7.
The word is based on the product as sold. A concentrate and its diluted spray can differ in hazard, which is one reason labels set mixing directions. Follow them exactly.
It also does not reflect the whole picture of a pest company’s treatment, such as where and how much was applied. For that, read the label and ask what was used.
Cost and signal words
We do not list prices, and signal words do not set them. They can shape cost indirectly.
Higher-toxicity products may require more protective equipment, a longer re-entry interval or a licensed applicator, which can affect how a company prices a job.
Restricted use products may be applied only by certified applicators or people they supervise 11.
When comparing quotes, ask whether a lower-toxicity option exists for your pest. Our cost guide covers how quotes are built, and our IPM guide explains choosing the least-risky effective control.
Using the signal word to choose and handle a product
- Identify the pest first. The EPA says to be certain of the problem before choosing a product 7.
- Compare signal words. The EPA advises choosing the least-toxic pesticide that will do the job 7.
- Read the precautions that match the word. Protective gear and keep-away directions follow from the hazard 7.
- Store by hazard. All products go in the original container, locked away from children 7.
- Plan for exposure. Keep the label handy, since Poison Control will ask for the product name and EPA Reg. No. 10.
DANGER products and emergencies
The EPA says DANGER products should be used with extreme care because they can severely burn skin and eyes 7. Leave them to licensed professionals unless the label clearly allows home use.
Call 911 if someone is unconscious, having trouble breathing or having convulsions; otherwise call Poison Control at 1-800-222-1222 with the EPA registration number ready 10.
Ongoing habits
- Keep products in original containers so the signal word stays visible 7.
- Store DANGER and WARNING products locked and separate from food, feed and children’s areas.
- Recheck the label when you buy a new batch; formulations and labels can change 7.
- Keep a list of products at home with their signal words and EPA Reg. Nos.
- Dispose of products you no longer need per the label; see pesticide storage and disposal.
Read the word in context
After the signal word, the label states the hazard, such as “Harmful if swallowed.” The EPA ties those statements to the toxicity category 2. Read them together.
Warning signs
- A product with POISON and a skull and crossbones being used in a home without a licensed applicator.
- A label that shows different signal words in different places, which federal rules do not allow 1.
- An ad that calls a CAUTION product “nontoxic” or “safe,” which label rules bar 4.
- Symptoms after use, such as eye pain, skin burns, coughing or nausea, which can point to pesticide poisoning.
- Any product in an unlabeled container 6.
The federal rules behind signal words
40 CFR 156.64. Category I requires DANGER on the front panel; Category II, WARNING; Category III, CAUTION. Category IV products need no signal word, and if one is used it must be CAUTION.
Where Category I is based on oral, inhalation or dermal toxicity, “Poison” must appear in red with the skull and crossbones nearby. A product may not bear different signal words on different parts of the label 1.
40 CFR 156.60 and 156.66. Front-panel warnings must be grouped and prominent; “Keep Out of Reach of Children” is required on nearly all products and placed near the signal word 2.
EPA Label Review Manual, Chapter 7 (March 2018). Explains how reviewers pick the word, including the 4% methanol rule 2. Chapter 3 sets minimum type sizes 3.
Spanish labels (PRIA 5). Key health and safety parts of pesticide labels must be translated into Spanish on a schedule that runs from December 29, 2025 for restricted use and Category I agricultural products to December 29, 2030 for everything else 9.
States. States enforce label rules and license applicators; see pest control licensing.
EPA signal words vs OSHA GHS signal words
| Feature | EPA pesticide label | OSHA SDS (GHS) |
|---|---|---|
| Words used | DANGER, WARNING, CAUTION 2 | DANGER, WARNING 8 |
| Basis | EPA toxicity categories I–IV 2 | GHS hazard classes 3 |
| Pictograms | Skull and crossbones; flame for some flammables 8 | Wider GHS set, e.g. exclamation mark, corrosion 8 |
| Governs product use? | Yes, the label is binding 7 | No 3 |
Because the systems differ, the EPA notes an SDS may carry a signal word that differs from the label’s 3. For use decisions, follow the label. See also EPA-registered pesticide.
Myths about signal words
- Myth CAUTION means the product is safe.
- Reality CAUTION marks Category III, low but not zero acute toxicity; NPIC says any product can poison at high doses 5.
- Myth No signal word means no hazard.
- Reality It means Category IV for every route, the lowest level, not no risk 2.
- Myth DANGER always comes with a skull and crossbones.
- Reality Only when Category I is due to oral, dermal or inhalation toxicity; eye or skin irritation alone gives DANGER without POISON 2.
- Myth The signal word covers bees and fish.
- Reality Environmental risks are in a separate label section 7.
- Myth The SDS and label must show the same word.
- Reality They use different systems and can differ 3.
Do signal words vary by state?
No. Signal words are set by federal regulation (40 CFR 156.64) and are the same on a product in every state 1.
What varies is who may buy and apply higher-hazard products, which states control through applicator certification and licensing, and some state-only product restrictions.
Spanish translations of key label safety text are being phased in nationwide under the federal PRIA 5 schedule 9.
When signal words matter to you
Use the signal word as a first filter. For home use, especially indoors or around children and pets, prefer the lowest signal word that is labeled for your pest. Leave DANGER products to licensed professionals unless the label plainly allows your use.
When hiring a company, ask for each product’s name, EPA Reg. No. and signal word, and ask why it was chosen. Our guide to choosing a pest control company lists more questions.
Quick decision guide
With CAUTION or no word, still read and follow the full label. With WARNING, take extra care with gear and storage. With DANGER or POISON, most homes should leave the job to a licensed professional. After any exposure, call Poison Control.
Questions about Pesticide Signal Words
What are the three pesticide signal words?
The three signal words are DANGER, WARNING and CAUTION. DANGER marks Toxicity Category I, the highest acute hazard; WARNING marks Category II; CAUTION marks Category III. Products in Category IV for every exposure route need no signal word, though they may use CAUTION. The rule is set in 40 CFR 156.64.
Which signal word is the most toxic?
DANGER is the most toxic. It marks Toxicity Category I. When that rating comes from oral, skin or breathing toxicity, the label must also show “POISON” in red with a skull and crossbones. The EPA says DANGER products can severely burn skin and eyes and should be used with extreme care.
Does CAUTION mean a pesticide is safe?
No. CAUTION marks Toxicity Category III, the lowest of the three signal words, but it still means a product can cause harm. NPIC notes any product can poison at high doses. Federal rules also bar labels from claiming a product is safe or nontoxic. Follow every label direction.
How is the signal word decided?
The EPA looks at five short-term toxicity tests: swallowing, skin contact, breathing, eye irritation and skin irritation. Each gets a category from I to IV. The signal word follows the most severe category. The EPA also recommends DANGER for products with 4% or more methanol.
What does “DANGER – POISON” with a skull and crossbones mean?
It means the product is in Toxicity Category I because of high toxicity if swallowed, absorbed through skin or inhaled. Federal rules require “Poison” in red on a contrasting background, with the skull and crossbones close by. Products rated DANGER only for eye or skin irritation do not carry the POISON symbol.
Why does a pesticide have no signal word?
A product rated Toxicity Category IV, the lowest level, for every exposure route, and negative for skin sensitization, is not required to carry a signal word. If it uses one, it must be CAUTION. No signal word still does not mean no risk, and the label still applies.
Do signal words tell you about long-term effects?
No. Signal words are based on acute, short-term toxicity tests. They do not rate long-term health effects, harm to bees or fish, or how well a product works. Environmental hazards and other precautions are in separate label sections, and more detail is on the safety data sheet.
Why is the signal word on the SDS different from the label?
Because the SDS follows OSHA’s Globally Harmonized System, which uses DANGER and WARNING under its own criteria, while the EPA uses DANGER, WARNING and CAUTION under its toxicity categories. The EPA notes the two can differ. For how to use a pesticide, follow the EPA label.
Where is the signal word on a pesticide label?
On the front panel, on its own line near “Keep Out of Reach of Children,” in capital letters.
It appears again at the start of the “Hazards to Humans and Domestic Animals” section.
Minimum type size depends on the panel size, from 6 point on small labels to 18 point on panels over 30 square inches.
Sources
- 40 CFR 156.64, Signal word (via Cornell Legal Information Institute), retrieved .
- U.S. EPA, Label Review Manual, Chapter 7: Precautionary Statements (March 2018), retrieved .
- U.S. EPA, Label Review Manual, Chapter 3: General Labeling Requirements (March 2018), retrieved .
- U.S. EPA, Label Review Manual, Chapter 12: Labeling Claims (November 2013), retrieved .
- National Pesticide Information Center, Signal Words fact sheet, retrieved .
- National Pesticide Information Center, Read the Label First, retrieved .
- U.S. EPA, Citizen’s Guide to Pest Control and Pesticide Safety (August 2017), retrieved .
- U.S. EPA, Pesticide Labels and GHS: Comparison and Samples, retrieved .
- U.S. EPA, Bilingual Labeling, retrieved .
- U.S. EPA, In Case of Pesticide Emergency, retrieved .
- U.S. EPA, Restricted Use Products (RUP) Report, retrieved .
Expert review
Written by the HyrePest Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Signal word rules quote 40 CFR 156.64; selection method, the methanol rule and the five worked examples come from EPA Label Review Manual Chapter 7 (Table 2); type sizes from Chapter 3; category cut-offs from NPIC’s fact sheet, flagged as last reviewed in 2008.
The GHS comparison follows EPA’s GHS page. Held for a toxicologist’s review before indexing.
Suggest a correction. We fix errors and say what changed.