Few pairs of polycrests are confused as often as Arsenicum album and Nux vomica. Both are chilly and worse from cold. Both can present as meticulous, orderly, fastidious patients. Both turn up repeatedly in cases of anxiety, indigestion, and disturbed sleep — the very presentations where a practitioner most often has to choose between two near-neighbours. Yet the remedies sit on opposite sides of a single emotional axis. The core difference is mental: Arsenicum Album's restlessness is driven by anxiety and fear of death, while Nux Vomica's is driven by irritability and anger — both can be fastidious and chilly, which is why they are so often confused. This guide is written for practitioners and students who have narrowed a case to these two and need the deciding distinctions: the keynotes, the mental split, the modalities, and the repertory rubrics that resolve the choice.
Arsenicum Album vs Nux Vomica at a glance
The fastest way to orient a differential is to lay the two pictures side by side. The table below summarises the distinctions that most often decide the prescription. Read it as a map of where to look in the case, not as a substitute for taking the totality.
| Arsenicum Album | Nux Vomica | |
|---|---|---|
| Core mental state | Anxiety, fear of death and disease; despair of recovery | Irritability, impatience, anger; quarrelsome |
| Restlessness type | Anxious and exhausted — too weak to move, too fearful to be still | Tense and wound-up — overstimulated, spasmodic, wants to be left alone |
| Fastidiousness | From anxiety and the need for control | From anger when order is disturbed |
| Temperature / chill | Markedly chilly; worse cold, better warmth | Markedly chilly; worse cold and draught, better warmth |
| Key time aggravation | After midnight, especially 1–2 a.m. | Wakes around 3–4 a.m.; worse in the morning |
| GI picture | Burning pains relieved by warmth; simultaneous vomiting and diarrhoea; prostration | Indigestion from overindulgence; ineffectual urging; constipation; retching |
| Reaction to food / stimulants | Worse from spoiled food; worse the sight or smell of food | Worse from rich food, alcohol, coffee, stimulants and drugs |
| Better from | Warmth, warm drinks, company | Warmth, rest, a nap, loosening clothing |
| Worse from | Cold, being alone, after midnight, exertion | Stimulants, mental overwork, early morning, cold air, noise |
| Company | Wants company for reassurance | Wants to be left alone; sensitive to disturbance |
The single biggest split is emotional. Strip away the shared chilliness and fastidiousness, and you are left with two opposite engines: anxiety drives Arsenicum, anger drives Nux Vomica. The Arsenicum patient is frightened — of illness, of death, of being left alone with the fear. The Nux Vomica patient is exasperated — with people, with delays, with anything that gets in the way of the work they are driving themselves through. Hold that contrast in mind and almost every other distinction in the case begins to fall into place.
The mental and emotional split — anxiety vs irritability
The mental picture is where this differential is won or lost. Both remedies are intense, both are highly strung, but the quality of the intensity is entirely different.
Arsenicum: anxiety and fear. The Arsenicum patient carries a deep, articulate fear that something is fundamentally wrong — that the illness is more serious than anyone admits, that recovery is impossible, that death is near. The restlessness flows directly from this fear: they move from bed to chair and back not because they have energy but because they are too anxious to stay still. They want company, not for conversation but for the security of another person's presence. H. C. Allen condensed the remedy into four words — restlessness, burning, prostration, midnight aggravation — and three of those four are anchored in the anxious, exhausted mental state. The Arsenicum keynotes are emotional first and physical second.
Nux Vomica: irritability and anger. The Nux Vomica patient is the irritable, impatient, easily angered overworker. Boericke describes the type as zealous, fiery, and inclined to abuse those around them; the patient is oversensitive to every external impression — noise, odours, light, music — and reacts to disturbance with anger rather than fear. This is the "ardent" character who drives themselves hard through mental work, props the system up with coffee, alcohol, tobacco, and stimulant medication, and then breaks down into a state of spasmodic oversensitivity and digestive revolt. The Nux Vomica patient does not want company; they want to be left alone, and they resent being disturbed.
The fastidiousness trap. This is the single most confused point in the entire differential, and it deserves to be spelled out. Both remedies are tidy, orderly, particular patients — so the bare observation "fastidious" does not separate them. The reason for the fastidiousness does. Arsenicum is fastidious out of anxiety: order is a defence against a world that feels dangerous, and disorder triggers fear that something terrible will happen. Nux Vomica is fastidious out of anger: disorder is an affront, an irritation, something that should not be allowed, and the patient is annoyed rather than frightened when things are out of place. When you find a meticulous patient and cannot tell which remedy it is, ask what they feel when order breaks down. Fear points to Arsenicum; irritation points to Nux Vomica.
Restlessness — the keynote both share, and how to read it
Restlessness appears in both pictures, and a beginner repertorising "restlessness" alone will get a muddy result. The skill is to read the kind of restlessness from the rest of the case.
Arsenicum's anxious, exhausted restlessness
Arsenicum's restlessness is the restlessness of fear in a depleted body. The patient is prostrated — genuinely weak, often more depleted than the apparent pathology would explain — yet they cannot lie still. They shift position constantly, move from bed to chair, toss and turn at night, driven by an anxiety they cannot settle. The paradox of being too exhausted to move and too frightened to rest is highly characteristic. Crucially, this restless patient wants someone with them. Solitude intensifies the fear; company is a partial relief.
Nux Vomica's tense, irritable restlessness
Nux Vomica's restlessness is the restlessness of an over-wound nervous system. The picture is of a patient whose sensory apparatus is on a hair-trigger — startled and aggravated by noise, light, smells, the slightest touch — and whose body tends to spasm and cramp. The restlessness here is tension seeking discharge rather than fear seeking reassurance. And the social direction is the opposite of Arsenicum: the Nux patient wants to be left alone, becomes more irritable when fussed over, and resents being disturbed. When restlessness comes packaged with oversensitivity and a desire for solitude, think Nux; when it comes with prostration and a desire for company, think Arsenicum.
Physical and clinical differentiation
Once the mental axis is clear, the physical generals and particulars confirm it. The gastrointestinal sphere is the most common decision point in practice, so it is worth taking slowly.
Gastrointestinal — the most common decision point
Arsenicum. The Arsenicum stomach is a burning stomach, and the burning is relieved by warmth — warm drinks, a warm application, a warm room. The classic acute picture is gastroenteritis or food poisoning: violent vomiting and diarrhoea, often simultaneous, with burning pains and prostration out of proportion to the apparent severity. The patient is anxious, chilly, thirsty for small frequent sips of warm water, and made worse by the sight or smell of food. The keynote causation is spoiled, contaminated, or tainted food — the body reacting to something that has gone bad.
Nux Vomica. The Nux stomach is the stomach of overindulgence. The trouble follows too much rich or spicy food, too much alcohol, too much coffee, too many stimulants or drugs — the digestive cost of the driven, intemperate lifestyle. The hallmark is ineffectual urging: constant, unsatisfactory desire for stool, the sense of always needing to go yet never finishing, with constipation and frequent fruitless urging. There is retching and nausea after eating, a sensitive epigastrium, and the characteristic feeling that the patient would feel better if only they could vomit but cannot quite manage it. Sour or bitter taste, a heavy load in the stomach an hour or so after eating, and morning nausea round out the picture.
A practical tie-break: spoiled food points to Arsenicum; too much food, drink, or stimulants points to Nux Vomica. If burning relieved by warmth dominates, lean Arsenicum; if ineffectual urging and a history of overindulgence dominate, lean Nux.
Sleep and time modalities
Time of aggravation is one of the cleanest separators of these two remedies. Arsenicum Album aggravates after midnight (especially 1–2 a.m.), whereas Nux Vomica characteristically wakes the patient around 3–4 a.m. with a morning aggravation; Nux is also listed in the materia medica as an antidote to Arsenicum.
The Arsenicum patient is the classic after-midnight case: anxious waking in the small hours, often between one and two, with fear, restlessness, and a need for company. The Nux Vomica sleep pattern is different in both timing and texture — the patient wakes around three or four in the morning, lies awake with the mind running (frequently on work and worries), then finally falls into a heavy, unrefreshing sleep just as it is time to get up, waking irritable and worse in the morning. When the case offers a precise nocturnal timing, use it: 1–2 a.m. with anxiety is an Arsenicum signature; 3–4 a.m. waking with morning aggravation is a Nux Vomica signature.
Temperature, discharges and general modalities
Temperature does not separate these remedies — and this is precisely why it is such a common trap. Both are markedly chilly, both are worse from cold (Nux is especially sensitive to draughts and uncovering), and both are better from warmth. The distinction lives in the mental state and the time modality, not the thermal general.
What does differentiate at the level of the particulars is the character of the discharges and the affected systems. Arsenicum's discharges are thin, acrid, burning, and excoriating — they corrode the tissues they touch, burning the nostril or the margin of an ulcer, and the remedy has a well-known tendency to right-sided complaints. Nux Vomica's picture is dominated less by acrid discharge and more by spasm, cramp, and sensory overload, with a strong affinity for the liver and portal congestion — the sluggish, overloaded digestion of the sedentary overworker. Where Arsenicum corrodes, Nux constricts.
Relationship between the two remedies
The classical relationships clarify how the two remedies behave together — and warn against a common prescribing error. Arsenicum and Nux Vomica are listed as mutual antidotes and as remedies that may follow one another, but they are not complementary. In practice this means two things. First, Nux Vomica can be used to antidote Arsenicum (and vice versa) — useful to know when judging the after-effects of a prescription. Second, and more importantly for case management, do not prescribe them in close sequence expecting them to build on each other the way a complementary pair would. They are near-neighbours that antidote, not partners that reinforce; treat the relationship as a differential to resolve, not a series to run.
Repertory rubrics that separate them
A differential is only as good as your ability to translate it into rubrics. The skill that resolves Arsenicum versus Nux Vomica is the same one that resolves every close differential: take the confirmed keynotes from the materia medica and cross-check them against the grades each remedy carries in the repertory. This is the heart of cross-checking materia medica against the repertory. The rubrics below are the ones that pull the two apart most reliably.
Where Arsenicum should lead:
- Mind; FEAR; death, of — a core Arsenicum rubric; Nux does not own this fear in the same way.
- Mind; ANXIETY; midnight, after — anchors both the anxiety and the time modality.
- Mind; RESTLESSNESS; anxious — the fear-driven restlessness, distinct from mere agitation.
- Stomach; BURNING; warm drinks amel. — the burning-relieved-by-warmth keynote.
- Generalities; MIDNIGHT, after; agg. — the 1–2 a.m. aggravation.
Where Nux Vomica should lead:
- Mind; IRRITABILITY and Mind; ANGER — the engine of the Nux picture.
- Mind; SENSITIVE; noise, to (and to odours, light) — the sensory overload.
- Rectum; URGING; ineffectual and Rectum; CONSTIPATION; ineffectual urging — the GI signature.
- Stomach; INDIGESTION; alcohol / coffee / rich food, from — the overindulgence causation.
- Sleep; WAKING; 3 a.m. with morning aggravation — the Nux time modality.
Where both remedies appear in a rubric — Chilly, Fastidious, Restlessness — that rubric confirms neither and should not be used to decide. The discriminating rubrics are the ones above, where the grades diverge sharply. Building the analysis around the symptoms that separate, rather than the ones the remedies share, is the difference between a confident prescription and a coin-toss.
Quick reference — decision summary
A revision cheat sheet for examinations and clinic. If you see the symptoms on the left, think Arsenicum; on the right, think Nux Vomica.
Think Arsenicum Album if you see:
- Anxiety, fear of death, despair of recovery
- Restless from fear, prostrated, wants company
- Burning pains relieved by warmth
- Vomiting and diarrhoea together; cause is spoiled food
- Worse the sight or smell of food
- Aggravation after midnight, especially 1–2 a.m.
- Thin, acrid, excoriating discharges
Think Nux Vomica if you see:
- Irritability, impatience, anger, quarrelsomeness
- Restless from tension, oversensitive, wants to be left alone
- Indigestion from overindulgence — rich food, alcohol, coffee, stimulants
- Ineffectual urging; constipation with constant unsatisfactory desire
- "Would feel better if he could vomit"
- Wakes 3–4 a.m., worse in the morning
- Spasm, cramp, sensory overload; liver/portal congestion
Frequently Asked Questions
What is the main difference between Arsenicum Album and Nux Vomica?
The main difference is mental. Arsenicum Album's state is driven by anxiety — fear of death and disease, restlessness from fear, prostration, and a desire for company. Nux Vomica's state is driven by anger — irritability, impatience, oversensitivity to noise and odours, and a desire to be left alone. Both are chilly and both can be fastidious, but the emotional engine is opposite: fear in Arsenicum, anger in Nux.
Is Nux Vomica an antidote to Arsenicum Album?
Yes. In the classical materia medica the two remedies are listed as mutual antidotes and as remedies that may follow one another, but they are not complementary. Practically, this means one can be used to antidote the other, but they should not be prescribed in close sequence expecting them to reinforce each other's action.
Arsenicum or Nux Vomica for indigestion — how do practitioners decide?
The decision turns on causation and modality. A burning stomach relieved by warmth, simultaneous vomiting and diarrhoea, and a history of spoiled or contaminated food point to Arsenicum. Overindulgence in rich food, alcohol, coffee, or stimulants, together with ineffectual urging and a sensitive epigastrium, points to Nux Vomica. This is a question of differentiating the totality, not a self-treatment instruction — the full case still governs the prescription.
Are Arsenicum and Nux Vomica both chilly remedies?
Yes — both are markedly chilly, both are worse from cold, and both are better from warmth, with Nux especially sensitive to draughts. Because temperature is shared, it cannot decide between them. The distinction lies in the mental state and the time of aggravation, not the thermal general.
What time of night does each remedy aggravate?
Arsenicum Album characteristically aggravates after midnight, especially between 1 and 2 a.m., with anxious waking. Nux Vomica characteristically wakes the patient around 3–4 a.m., who then lies awake before falling into heavy, unrefreshing sleep and waking with a morning aggravation.
Are both remedies fastidious?
Yes, but for different reasons — and this is the most common source of confusion. Arsenicum is fastidious from anxiety and the need for control, because order defends against a world that feels dangerous. Nux Vomica is fastidious from anger, because disorder is an irritation that should not be tolerated. When a patient is clearly meticulous, ask whether disorder makes them frightened (Arsenicum) or annoyed (Nux Vomica).
Resolving the differential in practice
Differentials like this one are where case analysis is actually done. The mental axis — anxiety versus anger — sets the direction; the modalities, the gastrointestinal picture, and the nocturnal timing confirm it; and the repertory grades give the prescription its evidence. For the fuller single-remedy picture, see the full Arsenicum Album remedy profile, and for a wider view of how this pair sits among the top polycrest remedies every student should know. Sound structured case-taking and disciplined step-by-step repertorisation are what turn a confusing two-remedy case into a clear one.
Read the full classical entries: Clarke's Arsenicum Album and Boericke's Arsenicum Album, alongside Clarke's Nux Vomica and Boericke's Nux Vomica.
Confused between two near-neighbours like these? In Similia you can read Nux Vomica in Boericke's Materia Medica alongside Clarke, Kent, Allen, and Hering, comparing more than 20 materia medica sources side by side for any remedy. You can then search the rubrics that separate these remedies and run both candidates against the same repertory grades in seconds — semantic search maps your case language ("restless from fear" versus "irritable, overworked") to the right rubric, and AI case analysis surfaces the differentiating symptoms automatically. Compare any two remedies free in Similia's repertory and materia medica.
