Allergic Reactions

What is an allergic reaction?

An excessive immune response to a normally harmless substance.

What is an antigen?

A foreign substance that triggers an immune response.

What is an allergen?

An antigen that triggers an allergic response.

What are antibodies?

Proteins produced by the immune system that recognize and bind specific antigens.

Which hypersensitivity type is most associated with common immediate allergies?

Type I or immediate hypersensitivity.

What antibody is central to Type I allergic reactions?

IgE.

What cells commonly carry IgE in Type I reactions?

Mast cells and basophils.

What happens when IgE binds an allergen during a repeat exposure?

Mast cells and basophils release inflammatory mediators such as histamine.

What major inflammatory mediators are mentioned in this course?

Histamine, prostaglandins, and leukotrienes.

What is sensitization?

The initial exposure process in which the immune system creates allergen-specific IgE for future exposures.

Why can repeated exposure cause a more severe reaction?

The patient is already sensitized and IgE-bound mast cells can react rapidly.

What is a local allergic reaction?

A reaction limited to a small area of the body.

What is a systemic allergic reaction?

A reaction involving multiple areas or body systems.

Can a local reaction progress to a systemic reaction?

Yes.

What is anaphylaxis?

A severe, rapidly developing systemic allergic reaction that can cause airway compromise, respiratory distress, hypotension, and shock.

What does histamine do to the skin?

Causes itching, hives, redness, and swelling.

What does histamine do to the airways?

Causes bronchoconstriction and increased mucus production.

What cardiovascular effects can histamine cause?

Vasodilation and increased vascular permeability, which can lower blood pressure.

What GI effects can occur from allergic mediator release?

Abdominal pain, nausea, vomiting, and other GI upset.

Why can anaphylaxis cause shock?

Widespread vasodilation and fluid leakage from blood vessels reduce effective circulating volume and blood pressure.

What findings are typical of a mild allergic reaction?

Localized itching, rash, hives, minor swelling, runny nose, or mild GI discomfort.

What findings suggest a moderate allergic reaction?

More widespread hives or flushing, swelling beyond the exposure site, mild wheezing or dyspnea, GI symptoms, and anxiety.

What findings suggest severe anaphylaxis?

Stridor, severe wheezing, respiratory distress, hypotension, shock, altered mental status, or severe GI symptoms.

Can anaphylaxis occur without skin findings?

Yes.

How quickly do allergic reactions usually begin?

Often within minutes to a few hours after exposure.

When do severe allergic reactions often peak according to this course?

Within about 3–30 minutes.

What is a biphasic allergic reaction?

A recurrence of allergic symptoms after an initial period of improvement.

How common does this course say biphasic anaphylaxis may be?

Up to about 20% of anaphylactic reactions.

Why is continued observation important after improvement?

Symptoms can recur in a biphasic reaction.

What common food allergens are emphasized?

Nuts, shellfish, milk, eggs, and other foods.

What insect-related allergens are emphasized?

Bee and wasp stings.

What medication allergens are emphasized?

Antibiotics and NSAIDs.

What environmental allergens are emphasized?

Pollen, pet dander, mold, and similar environmental triggers.

What factors can make an allergic reaction more severe?

Previous severe reactions, route of exposure, larger exposure amount, comorbidities, and medications.

Which exposure routes may cause more severe allergic reactions than skin contact?

Ingestion and injection.

What is the first priority when approaching an allergic-reaction call?

Scene safety.

What scene hazards should be considered in allergic reactions?

Ongoing allergens such as bees, chemicals, foods, or other exposure sources.

When should ALS be considered early?

When the reaction appears severe or is rapidly progressing.

What is the top airway concern in allergic reactions?

Swelling that can obstruct the upper airway.

What breath sound suggests upper-airway swelling?

Stridor.

What breath sound suggests lower-airway bronchospasm?

Wheezing.

What circulation findings can suggest anaphylactic shock?

Rapid weak pulse, hypotension, pale cool clammy skin, and altered mental status.

What skin findings commonly occur in allergic reactions?

Hives, flushing, itching, and swelling.

Why is altered mental status concerning in an allergic reaction?

It may indicate severe hypoxia or shock.

What SAMPLE questions are especially important?

Known allergies, previous reaction severity, medications, EpiPen use, last oral intake, and timeline of events.

Why is last oral intake useful in an allergic reaction?

It may reveal a food trigger.

What OPQRST element is especially useful for allergic reactions?

Onset and time, because speed of progression helps indicate severity.

Why should vital signs be trended?

Allergic reactions can deteriorate quickly and trends reveal progression.

How often does this course suggest reassessing severe reactions?

About every 5 minutes.

How often does this course suggest reassessing milder reactions?

About every 15 minutes.

What should be documented about symptom progression?

When symptoms started, how they changed, and how quickly they progressed.

What multi-system pattern should raise concern for anaphylaxis?

Skin or mucosal findings plus respiratory compromise, hypotension/shock, or severe GI symptoms.

Can repeat anaphylaxis occur without hives?

Yes.

What respiratory features help distinguish anaphylaxis from isolated asthma?

Anaphylaxis may also include hives, swelling, GI symptoms, throat tightness, hypotension, or rapid onset after an allergen.

What is the treatment of choice for anaphylaxis?

Epinephrine.

If unsure between asthma and anaphylaxis in a patient with allergy exposure and systemic symptoms, what does this course recommend?

Use epinephrine first for suspected anaphylaxis, then bronchodilator if indicated.

What conditions can mimic an allergic reaction?

Asthma, panic attacks, myocardial infarction, pulmonary embolism, toxin exposure, and other causes of shock or airway problems.

What is the main treatment approach for a mild allergic reaction?

Remove the allergen if safe, observe, monitor, provide comfort, and use antihistamines if allowed by protocol.

What simple treatment can help localized itching and swelling?

Cold compresses.

Should vomiting be induced after a food allergen exposure?

No, unless specifically directed by medical control.

How should an insect stinger be removed according to this course?

Scrape it out rather than squeezing it with tweezers.

What should be done for a chemical allergen on the skin?

Remove contaminated clothing and rinse the area.

What should be done if a medication causes the reaction?

Stop the medication exposure and bring information about the medication to the hospital.

When is oxygen indicated in allergic reactions?

When there is respiratory distress or low oxygen saturation.

What oxygen saturation goal is emphasized in this course?

Above 94%.

What device may be used for mild oxygen needs?

Nasal cannula.

What device may be used for more severe oxygen needs?

Nonrebreather mask.

What may help allergic wheezing if allowed by protocol?

A bronchodilator such as albuterol.

What should be checked before assisting with a patient's own allergy medication?

That it is the patient's medication, the medication identity, and expiration if time permits.

What medication is first-line for anaphylaxis?

Epinephrine.

What findings indicate epinephrine in anaphylaxis?

Airway swelling or stridor, severe wheezing or breathing difficulty, shock, hypotension, altered mental status, or rapidly progressing symptoms.

What is the adult epinephrine auto-injector dose in this course?

0.3 mg.

What is the pediatric epinephrine auto-injector dose in this course?

0.15 mg.

What epinephrine dose does this course give for patients over 30 kg?

0.3 mg IM.

What epinephrine dose does this course give for children 15–30 kg?

0.15 mg IM.

What should be done for very small children when dosing is unclear?

Contact medical control and follow local protocol.

What epinephrine concentration is specified for anaphylaxis in this course?

1 mg/mL, also called 1:1000.

What is the preferred injection site for epinephrine?

The lateral or anterolateral thigh.

Can an epinephrine auto-injector be given through clothing in an emergency?

Yes, through a single layer of clothing while avoiding seams and pockets.

How long should the auto-injector be held in place according to this course?

About 3–5 seconds.

What memorable EpiPen orientation phrase is given in the course?

Blue to the sky, orange to the thigh.

What are the five rights of medication administration?

Right patient, right drug, right dose, right route, and right time.

How often may epinephrine be repeated in this course if symptoms do not improve?

Every 5–15 minutes, according to protocol.

How many doses does this course say should generally not be exceeded without medical control?

About 2–3 doses.

What should happen after epinephrine administration?

Request or consider ALS, reassess frequently, monitor airway/breathing/circulation, and prepare for repeat dosing if needed.

How often should vitals be checked after epinephrine in severe anaphylaxis?

About every 2–5 minutes.

What common epinephrine side effects are emphasized?

Tachycardia, hypertension, and anxiety.

Are tachycardia or anxiety reasons to withhold epinephrine in true anaphylaxis?

No.

Why are beta-blocker patients a special concern?

They may respond less effectively to epinephrine.

Should patients with heart disease still receive epinephrine for true anaphylaxis?

Yes, with close monitoring.

Should pregnant patients with true anaphylaxis receive epinephrine?

Yes; the benefits outweigh the risks.

What position may help a hypotensive anaphylaxis patient?

Supine with legs elevated if tolerated.

What position may help a patient with major breathing difficulty?

Sitting upright if tolerated.

Should a patient with anaphylaxis stand or walk around?

No.

What additional respiratory medication may be used if wheezing persists and protocol allows?

A bronchodilator.

Are antihistamines first-line treatment for anaphylaxis?

No. Epinephrine is first-line.

Are steroids first-line treatment for anaphylaxis?

No. Epinephrine is first-line.

Why is rapid transport important in anaphylaxis?

Symptoms can progress or recur and advanced airway or circulatory support may be needed.

What should be communicated in a prenotification for anaphylaxis?

That the patient has anaphylaxis, current airway/breathing/circulation findings, treatments, response, and ETA.

Why should anaphylaxis gear stay within reach during transport?

The patient may deteriorate or need repeat epinephrine.