Start with the pattern
A known exposure helps, but it is not always available. Vaccines, medications, insect stings, and other exposures may raise suspicion. The inciting event can also be unknown or unwitnessed.
Start with the timeline. Acute hypersensitivity should have a peracute onset, with relevant signs developing within minutes to a few hours. Signs that accumulate gradually over a longer period fit less well, so consider other causes. RECOVER uses peracute onset as an early branch in its recognition algorithm.
Ask four questions first
- Did the signs develop within minutes to a few hours?
- Is there a known or possible recent exposure?
- Which organ systems are involved now?
- Is there collapse, hypotension, or severe respiratory distress?
The overall pattern matters more than one isolated finding.
Count the non-cutaneous systems involved
RECOVER considers three non-cutaneous systems when assessing suspected acute hypersensitivity. Count the systems involved, then weigh that count alongside timing, skin findings, exposure context, and severity.
Gastrointestinal
Persistent or repeated vomiting or diarrhea, or abdominal pain, supports GI involvement. A mild, isolated, self-limiting GI episode is treated differently in the framework.
Respiratory
Increased effort, stridor, and wheezing can signal respiratory involvement. Severe respiratory distress changes the pathway.
Cardiovascular
Pallor, an abnormal heart rate, hypotension, or collapse can signal cardiovascular involvement.
The three main pathways
Use the severity of the presentation to choose the treatment direction, then reassess as the patient responds.
Uncomplicated allergic reaction
A peracute presentation dominated by cutaneous signs such as urticaria, angioedema, flushing, or pruritus. A mild, isolated GI episode can still fit. Meaningful respiratory or cardiovascular compromise should not be present.
RECOVER treatment direction: H1 receptor antagonist with supportive care as indicated.
Moderate anaphylaxis
The peracute pattern supports anaphylaxis, typically with signs in two or more body systems, including non-cutaneous involvement. There is no collapse, hypotension, or severe respiratory distress. Without skin signs, look for additional supporting evidence.
RECOVER treatment direction: IM epinephrine as early as possible, with appropriate supportive care.
Severe anaphylaxis
Collapse, hypotension, or severe respiratory distress changes the pathway, even when other parts of the picture are incomplete.
RECOVER treatment direction in hospital: continuous IV epinephrine infusion with appropriate supportive care, rather than relying on IV bolus treatment. The algorithm targets a mean arterial pressure of 70 mmHg.
Feline exception: A cat with severe respiratory distress may not tolerate IV catheter placement. If IV access and an epinephrine infusion are not possible, RECOVER considers IM epinephrine a reasonable bridge in this situation.
Working through a suspected reaction?
The Anaphylaxis Protocol helps you apply the recognition pathway to the individual patient, then keeps treatment and reassessment in the same workflow.
No skin signs? Do not stop there.
Skin findings can make acute hypersensitivity easier to recognize, but they are not required for anaphylaxis. A patient may have a peracute GI, respiratory, or cardiovascular pattern without obvious urticaria, angioedema, flushing, or pruritus.
When skin signs are absent, look for findings that support the overall diagnosis:
- A known or suspected recent exposure
- A previous hypersensitivity reaction
- A retained insect stinger
- Gallbladder wall edema on point-of-care ultrasound
- Unexplained peritoneal effusion
- Otherwise unexplained hemoabdomen
None is a stand-alone diagnostic test. RECOVER acknowledges how difficult recognition becomes when both the allergen and skin signs are absent, and recommends seeking supporting evidence when non-cutaneous systems are involved.
The absence of skin signs does not rule out anaphylaxis.
When the pattern is still uncertain
Not every peracute collapse, vomiting episode, or respiratory event is anaphylaxis.
Without skin signs, a clear exposure, or supporting findings, anaphylaxis may still be possible, but other differentials deserve active consideration. A near-simultaneous change across systems over minutes to a few hours fits acute hypersensitivity better than signs that accumulate over many hours or days.
RECOVER's algorithm is intended for patients in whom acute hypersensitivity is already suspected. It should not be applied to every multisystem presentation.
The guideline includes 12 treatment recommendations. Seven draw on low or very low quality evidence, and five are based on expert opinion. Keep that uncertainty in mind when applying the pathway to a patient.
A quick way to organize the decision
| Presentation | Pathway | Treatment direction |
|---|---|---|
| Peracute cutaneous signs without meaningful non-cutaneous involvement | Uncomplicated allergic reaction | H1 receptor antagonist |
| Anaphylaxis without collapse, hypotension, or severe respiratory distress | Moderate anaphylaxis | Early IM epinephrine |
| Anaphylaxis with collapse, hypotension, or severe respiratory distress | Severe anaphylaxis | Continuous IV epinephrine infusion in hospital |
RECOVER grades these presentations around treatment-relevant distinctions instead of treating every acute allergic presentation as the same problem.
Two treatment priorities worth remembering
Antihistamines do not replace epinephrine in anaphylaxis
H1 receptor antagonists belong to the uncomplicated allergic reaction pathway. Once the presentation meets an anaphylaxis pathway, epinephrine becomes the treatment priority in RECOVER's framework.
Routine systemic glucocorticoids are not recommended for anaphylaxis
RECOVER recommends against routine systemic glucocorticoids in dogs and cats with anaphylaxis. This is a strong recommendation based on very low quality evidence. It also suggests against their routine use in uncomplicated allergic reactions.
The first intervention is not the end of the workflow
Once the initial pathway is clear, the case becomes patient-specific. Species, weight, severity, vascular access, perfusion, and response to treatment can all affect what happens next.
Keep the clinical sequence visible:
RecognizeTreatReassessFollow up
The patient may improve, remain unchanged, or deteriorate. Each response calls for a fresh assessment.
Use the framework. Then run the patient.
The guide helps you identify which acute hypersensitivity pathway fits. When you need to apply it to a specific dog or cat, the protocol keeps recognition, treatment, reassessment, and follow-up connected in one workflow.
Quick FAQ
Does anaphylaxis require skin signs?
No. Cutaneous findings can help with recognition, but anaphylaxis may occur without them. Timing, affected organ systems, exposure context, severe features, and other supporting findings matter more when skin signs are absent.
Does the allergen need to be known?
No. Exposure may be unwitnessed. RECOVER keeps acute hypersensitivity in consideration when the peracute presentation is compatible, even without a known trigger.
Does vomiting automatically mean anaphylaxis?
No. RECOVER distinguishes mild, isolated GI signs from persistent or repeated gastrointestinal involvement. The rest of the pattern still matters.
Are antihistamines first-line treatment for anaphylaxis?
No. H1 receptor antagonists are used for uncomplicated allergic reactions in the RECOVER framework. Moderate and severe anaphylaxis follow epinephrine-based pathways.
What about corticosteroids?
RECOVER recommends against routine systemic glucocorticoids in anaphylaxis and suggests against their routine use in uncomplicated allergic reactions.
References
- Burkitt-Creedon JM, Mandell DC, Thawley VJ, et al. RECOVER Guidelines: First Aid. Evidence, Treatment Recommendations, Knowledge Gap Analysis, and Clinical Guidelines for Acute Allergy and Anaphylaxis in Dogs and Cats. Journal of Veterinary Emergency and Critical Care. 2026;36:S63-S89. doi:10.1111/vec.70137.
- Smith MR, Wurlod VA, Ralph AG, Daniels ER, Mitchell M. Mortality rate and prognostic factors for dogs with severe anaphylaxis: 67 cases (2016-2018). Journal of the American Veterinary Medical Association. 2020;256:1137-1144.
Disclaimer
This guide is for veterinary professional education and clinical workflow support. It summarizes selected parts of the 2026 RECOVER First Aid framework for acute allergy and anaphylaxis in dogs and cats.
It does not replace emergency stabilization, patient assessment, differential diagnosis, continuous monitoring, current product information, local regulations, current references, or clinical judgment. The evidence for several RECOVER recommendations is limited, and the guideline identifies important knowledge gaps.