Poison and Disease Rules

Poison and disease represent two distinct categories of ongoing harm in Dungeons & Dragons 5th Edition, each governed by separate mechanical frameworks that interact with saving throws, conditions, and hit point damage in structured ways. These rules appear across combat encounters, exploration hazards, and monster abilities, making them among the most frequently referenced subsystems at the table. The mechanics described here apply to the core 5th Edition ruleset as published by Wizards of the Coast in the Player's Handbook and Dungeon Master's Guide.

Definition and scope

Within the 5th Edition ruleset, poison refers to both a damage type and a condition. As a damage type, poison damage is dealt by venomous creatures, toxic substances, and specific spells. As a condition, the Poisoned condition imposes disadvantage on attack rolls and ability checks — a meaningful mechanical penalty covered in detail under Conditions Rules. The dual nature of poison means a creature can take poison damage without becoming Poisoned, or become Poisoned without taking poison damage, depending on the source and the saving throw outcome.

Disease is a broader narrative and mechanical category covering infections, curses of biological origin, and supernatural afflictions. Unlike poison, disease does not have a dedicated damage type; instead, individual diseases impose bespoke effects defined by their source — typically a monster stat block or an adventure's specific rules text.

Poison and disease both intersect with the Saving Throws Rules, almost exclusively Constitution saving throws, though specific sources may call for other ability scores.

How it works

Poison mechanics follow a structured resolution path:

1. A character is exposed to a poison source (attack, ingested substance, inhaled cloud, or contact).
2. The character makes a Constitution saving throw against a DC set by the poison's source (ranging from DC 10 for basic vials to DC 19 for powerful monster venoms such as the Giant Scorpion's).
3. On a failed save, the character suffers the poison's listed effect — typically some combination of poison damage (commonly expressed in dice such as 4d10) and the Poisoned condition.
4. Some poisons require repeated saving throws at set intervals (end of each turn, or once per hour) to either maintain or end the effect.
5. The Poisoned condition ends when cured by a lesser restoration spell, a herbalism kit antitoxin (granting advantage on the saving throw), or the natural resolution of the effect.

Disease mechanics are less standardized. The Dungeon Master's Guide (Wizards of the Coast, 2014) presents disease as a flexible DM-adjudicated system rather than a rigid ruleset. A typical disease resolution path includes:

1. Exposure (usually from a monster attack, contaminated environment, or narrative event).
2. An incubation saving throw (Constitution, DC varies by disease — for example, Sewer Plague uses DC 11).
3. If failed, the disease's symptoms activate after an incubation period, often 1d4 days.
4. Subsequent saving throws (often once every 24 hours) determine whether the disease progresses, holds, or resolves.

The Exploration Rules and Traps and Hazards Rules both reference disease as an environmental consequence, particularly in dungeon and wilderness settings.

Common scenarios

Poison appears most frequently in these encounter contexts:

• Venomous creature attacks: Spiders, snakes, wyverns, and yuan-ti deliver poison through their natural attacks. The Giant Poisonous Snake, for example, deals 2d6 poison damage on a failed DC 11 Constitution save.
• Weapon poison: Assassins and thieves apply contact or injury poisons to bladed weapons using the crafting rules or purchased vials. The Dungeon Master's Guide lists 14 distinct poison types with costs ranging from 100 gp (Basic Poison) to 1,500 gp (Malice).
• Spell effects: Poison Spray (a cantrip) deals 1d12 poison damage on a failed Constitution save. Ray of Sickness adds the Poisoned condition for 1 round on a failed save.
• Environmental hazards: Gas-filled chambers, poisoned traps, and alchemical traps introduce poison as a hazard rather than a monster ability.

Disease scenarios include:

• Undead and fiend attacks: Mummy rot (inflicted by mummies) and the Cackle Fever disease (associated with gnolls in some sourcebooks) impose ongoing Constitution score damage and disadvantage on Wisdom checks.
• Wilderness survival: Contaminated water sources during extended travel introduce disease exposure rolls at DM discretion, connecting to Resting Rules and recovery mechanics.
• Narrative consequences: Failed social encounters in plague-ridden cities or dungeon environments saturated with necrotic energy may introduce disease as a story mechanic.

Decision boundaries

The critical mechanical distinction between poison and disease lies in reversibility and system ownership.

Dungeon Masters resolving ambiguous cases — such as whether a supernatural curse that sickens a character counts as a disease for spell targeting purposes — should default to whether the source description uses the word "disease." The lesser restoration spell explicitly cures "one disease or one effect that is causing the target to be Blinded, Deafened, Paralyzed, or Poisoned," making the classification consequential.

For broader context on how these subsystems connect to the full rules architecture, the DnD Core Rules Overview provides a structural map of all major rule categories. Tables building complex encounters with poison or disease should also reference the Encounter Building Rules to calibrate the mechanical weight of ongoing conditions against party resources. Readers seeking the foundational framework for how tabletop recreation mechanics are structured as a sector can consult How Recreation Works: Conceptual Overview and the site index for full topic navigation.

References

• Player's Handbook, 5th Edition — Wizards of the Coast (Appendix A: Conditions; Chapter 8: Adventuring)
• Dungeon Master's Guide, 5th Edition — Wizards of the Coast (Chapter 8: Running the Game — Diseases and Poisons)
• D&D Beyond Rules Compendium — Wizards of the Coast (official digital rules reference for 5th Edition mechanics)
• Systems Reference Document (SRD) 5.1 — Wizards of the Coast / Creative Commons (open rules reference covering poison damage type and Poisoned condition)