Common Skin Reactions: Causes and Characteristics

Acute urticaria: This is a superficial swelling of the skin that results in a raised, red, itchy rash. Wheals are also often observed. It can appear anywhere on the body and develop quickly, usually following exposure to an allergen. Common triggers include viral infections, insect bites and stings, certain foods, and medications.

Erythema multiforme (EM): This is a hypersensitivity reaction that is usually triggered by a viral infection, with herpes simplex being the most common agent. The skin eruption associated with EM is typical of multiple ‘target lesions’ that comprise three concentric color zones and a dark/dusky center.

Acute angioedema: This is a skin reaction similar to urticaria, but it affects the deeper layers of the dermis and subcutaneous tissue. The mucous membranes are often affected, with the eyes or lips being the most common sites of swelling. Allergy is the most common cause of angioedema.

Erythema migrans: This is the most common skin manifestation of Lyme disease, which is a borrelia infection caused by infected ticks. Typically, the rash appears 7–14 days after the tick bite as a red papule or macule at the bite site. This then increases in size and is often described as a ‘bullseye’ lesion.

Stevens–Johnson syndrome: This is a rare, acute, severe, and potentially fatal skin reaction. It is the result of an unpredictable reaction to various medications, with antibiotics being the most common trigger. A flu-like prodromal illness is typically followed by the abrupt onset of a red rash. This rash spreads quickly all over the body and affects the mucous membranes before sheet-like skin and mucosal loss develops.

When discharging patients who have experienced anaphylaxis, a risk-stratified approach should be taken. The patient’s response to adrenaline and their symptoms are important factors to consider. The UK Resuscitation Council guidelines suggest that patients may be considered for fast-track discharge if they have had a good response to a single dose of adrenaline within 30 minutes of the reaction, their symptoms have completely resolved, they have been trained on how to use adrenaline auto-injectors, and there is adequate supervision following discharge. While the patient’s peak expiratory flow rate and serum tryptase levels should be measured, they are not specifically advised for risk-stratifying patients for discharge post-anaphylaxis according to the UKRC guidelines. Spirometry is also not specifically recommended for this purpose. However, patients with severe asthma or those who experienced severe respiratory compromise during the anaphylactic reaction should be observed for at least 12 hours after symptom resolution.

Anaphylaxis is a severe and potentially life-threatening allergic reaction that affects the entire body. It can be caused by various triggers, including food, drugs, and insect venom. The symptoms of anaphylaxis typically occur suddenly and progress rapidly, affecting the airway, breathing, and circulation. Common signs include swelling of the throat and tongue, hoarse voice, respiratory wheeze, dyspnea, hypotension, and tachycardia. In addition, around 80-90% of patients experience skin and mucosal changes, such as generalized pruritus, erythematous rash, or urticaria.

The management of anaphylaxis requires prompt and decisive action, as it is a medical emergency. The Resuscitation Council guidelines recommend intramuscular adrenaline as the most important drug for treating anaphylaxis. The recommended doses of adrenaline vary depending on the patient’s age, ranging from 100-150 micrograms for infants under 6 months to 500 micrograms for adults and children over 12 years. Adrenaline can be repeated every 5 minutes if necessary, and the best site for injection is the anterolateral aspect of the middle third of the thigh. In cases of refractory anaphylaxis, IV fluids and expert help should be sought.

Following stabilisation, patients may be given non-sedating oral antihistamines to manage persisting skin symptoms. It is important to refer all patients with a new diagnosis of anaphylaxis to a specialist allergy clinic and provide them with an adrenaline injector as an interim measure before the specialist assessment. Patients should also be prescribed two adrenaline auto-injectors and trained on how to use them. A risk-stratified approach to discharge should be taken, as biphasic reactions can occur in up to 20% of patients. The Resus Council UK recommends a fast-track discharge for patients who have had a good response to a single dose of adrenaline and complete resolution of symptoms, while those who require two doses of IM adrenaline or have a history of biphasic reaction should be observed for at least 12 hours following symptom resolution.

Types of Vaccines and Their Definitions

Live Attenuated Vaccine:
This type of vaccine involves injecting a small sample of the virus into the body, allowing the immune system to fight it and create an immune response against it for future attacks. The MMR vaccine is an example of a live attenuated vaccine.

Conjugate Vaccine:
Conjugate vaccines are created by combining a weak antigen with a strong antigen to produce a stronger immune response. Typically, a polysaccharide is joined with a strong protein to create this type of vaccine.

Inactivated Vaccine:
Inactivated vaccines, such as the pertussis and hepatitis A vaccines, contain dead pathogens that cannot cause disease but still stimulate an immune response.

Subunit Vaccine:
Subunit vaccines only contain the antigenic component of the pathogen. However, there is no guarantee that immunological memory will be achieved appropriately. The pneumococcal vaccine is an example of a subunit vaccine.

Toxoid Vaccine:
Toxoid vaccines are toxins that have been deactivated but still stimulate an immune response from the immune system. Examples include the diphtheria and tetanus vaccines.

Understanding the Different Types of Vaccines

Understanding Non-IgE-Mediated Cows’ Milk Protein Allergy

When a child presents with a combination of cutaneous and gastrointestinal symptoms, an allergy to cows’ milk protein is the most likely cause. This is especially true for infants who are being weaned onto cows’ milk, as in this case. However, it’s important to note that this type of allergy is often confused with lactose intolerance, which is a different condition altogether.

One key indicator that this is a non-IgE-mediated allergy is the presence of an eczematous rash rather than an immediate reaction following ingestion. This is in contrast to an IgE-mediated reaction, which would result in an urticarial rash and occur immediately after milk was ingested.

It’s also worth noting that this is not likely to be eczema, as the symptoms have not improved with emollients and there are accompanying gastrointestinal symptoms. Similarly, a peanut allergy can be ruled out as the symptoms do not fit the diagnosis of an IgE-mediated reaction.

Overall, understanding the nuances of non-IgE-mediated cows’ milk protein allergy is crucial for accurate diagnosis and effective treatment.

Types of Allergy Tests

Allergy tests are used to determine if a person has an allergic reaction to a particular substance. There are several types of allergy tests available, each with its own advantages and limitations. The most commonly used test is the skin prick test, which is easy to perform and inexpensive. Drops of diluted allergen are placed on the skin, and a needle is used to pierce the skin. A wheal will typically develop if a patient has an allergy. This test is useful for food allergies and pollen.

Another type of allergy test is the radioallergosorbent test (RAST), which determines the amount of IgE that reacts specifically with suspected or known allergens. Results are given in grades from 0 (negative) to 6 (strongly positive). This test is useful for food allergies, inhaled allergens (e.g. pollen), and wasp/bee venom.

Skin patch testing is useful for contact dermatitis. Around 30-40 allergens are placed on the back, and irritants may also be tested for. The patches are removed 48 hours later, and the results are read by a dermatologist after a further 48 hours. Blood tests may be used when skin prick tests are not suitable, for example if there is extensive eczema or if the patient is taking antihistamines. Overall, allergy tests are an important tool in diagnosing and managing allergies.

Shingles Vaccine Availability by Age

The shingles vaccine is available to individuals at different ages depending on their stage of life. Those who are 70 or 78-years old are eligible to receive the vaccine. However, it is not routinely offered to patients who are in their 50’s or 60’s. The vaccine is not part of the routine childhood immunisation schedule and is only available to NHS patients in their 70’s. It is not offered to individuals who are 80 or older, as it appears to be less effective in this age group. It is important to consult with a healthcare provider to determine the appropriate age to receive the shingles vaccine.

Although it is possible for the man to have been prescribed any of the medications listed, it is evident that he is experiencing angioedema, as indicated by the swelling of his tongue and lips. Ramipril, an ACE inhibitor, is the medication most commonly associated with this side effect. Even if the patient has no history of allergies or negative reactions to ACE inhibitors, angioedema can still occur. While the likelihood of this happening is low, it is important to keep in mind due to the large number of patients taking this type of medication and the potential complications associated with angioedema.

Angiotensin-converting enzyme (ACE) inhibitors are commonly used as the first-line treatment for hypertension and heart failure in younger patients. However, they may not be as effective in treating hypertensive Afro-Caribbean patients. These inhibitors are also used to treat diabetic nephropathy and for secondary prevention of ischaemic heart disease. The mechanism of action of ACE inhibitors is to inhibit the conversion of angiotensin I to angiotensin II. They are metabolized in the liver through phase 1 metabolism.

ACE inhibitors may cause side effects such as cough, which occurs in around 15% of patients and may occur up to a year after starting treatment. This is thought to be due to increased bradykinin levels. Angioedema may also occur up to a year after starting treatment. Hyperkalaemia and first-dose hypotension are other potential side effects, especially in patients taking diuretics. ACE inhibitors should be avoided during pregnancy and breastfeeding, and caution should be exercised in patients with renovascular disease, aortic stenosis, or hereditary or idiopathic angioedema.

Patients receiving high-dose diuretic therapy (more than 80 mg of furosemide a day) are at an increased risk of hypotension when taking ACE inhibitors. Before initiating treatment, urea and electrolytes should be checked, and after increasing the dose, a rise in creatinine and potassium may be expected. Acceptable changes include an increase in serum creatinine up to 30% from baseline and an increase in potassium up to 5.5 mmol/l. Patients with undiagnosed bilateral renal artery stenosis may experience significant renal impairment. The current NICE guidelines provide a flow chart for the management of hypertension.

Understanding Rare Genetic Disorders: DiGeorge’s Syndrome and Associated Features

DiGeorge’s syndrome, also known as 22q11.2 deletion syndrome, is a rare genetic disorder that affects the development of various organs in the body. One of the primary features of this syndrome is a decreased production and function of T-cells due to an absent or poorly developed thymus, leading to susceptibility to infections. Additionally, individuals with DiGeorge’s syndrome may experience hypocalcaemic tetany due to a failure of parathyroid development, which can be exacerbated by gastrointestinal infections.

Other features of DiGeorge’s syndrome include congenital cardiac defects, particularly those involving the great vessels, and the absence of a normal thymus. Serum immunoglobulin concentrations are often normal, but antibody responses may be impaired. T-cell levels are reduced, whereas B-cell levels are normal.

In addition to these medical features, individuals with DiGeorge’s syndrome may have characteristic facial features such as retrognathia or micrognathia, a long face, high and broad nasal bridge, narrow palpebral fissures, small teeth, asymmetrical crying face, downturned mouth, short philtrum, low-set and malformed ears, hypertelorism, and a dimple on the tip of the nose.

Overall, understanding the features and implications of rare genetic disorders like DiGeorge’s syndrome is crucial for proper diagnosis and management of affected individuals.

Antibiotics for Diarrhoeal Illnesses: Understanding the Appropriate Treatment

Giardiasis is a diarrhoeal illness caused by the protozoa Giardia lamblia, which is spread through contaminated food, water or faeces. The disease can last up to six weeks and presents with symptoms such as abdominal bloating, flatulence or malabsorption. Metronidazole is the preferred treatment for giardiasis due to its effectiveness and improved compliance.

Doxycycline is used to treat cholera, a severe disease that causes watery diarrhoea and dehydration. However, the chronic duration of symptoms and presence of parasitic organisms make cholera unlikely.

Ciprofloxacin is used to treat urinary-tract infections and some diarrhoeal illnesses such as cholera and Campylobacter jejuni infections. However, Campylobacter is usually self-limiting and has a much shorter duration of illness, making it an unlikely diagnosis.

Clindamycin is not classically used to treat giardiasis and should be used with caution due to the increased risk of developing antibiotic-associated colitis and opportunistic infections such as Clostridium difficile.

Co-amoxiclav may be used to treat intra-abdominal infections such as biliary sepsis, but it is not indicated for giardiasis.

In summary, understanding the appropriate use of antibiotics for diarrhoeal illnesses is crucial in providing effective treatment and avoiding unnecessary risks.

Patients who are immunosuppressed, such as those taking azathioprine, should not receive live attenuated vaccines including BCG, MMR, oral polio, yellow fever, and oral typhoid.

Types of Vaccines and Their Characteristics

Vaccines are essential in preventing the spread of infectious diseases. However, it is crucial to understand the different types of vaccines and their characteristics to ensure their safety and effectiveness. Live attenuated vaccines, such as BCG, MMR, and oral polio, may pose a risk to immunocompromised patients. In contrast, inactivated preparations, including rabies and hepatitis A, are safe for everyone. Toxoid vaccines, such as tetanus, diphtheria, and pertussis, use inactivated toxins to generate an immune response. Subunit and conjugate vaccines, such as pneumococcus, haemophilus, meningococcus, hepatitis B, and human papillomavirus, use only part of the pathogen or link bacterial polysaccharide outer coats to proteins to make them more immunogenic. Influenza vaccines come in different types, including whole inactivated virus, split virion, and sub-unit. Cholera vaccine contains inactivated strains of Vibrio cholerae and recombinant B-subunit of the cholera toxin. Hepatitis B vaccine contains HBsAg adsorbed onto aluminium hydroxide adjuvant and is prepared from yeast cells using recombinant DNA technology. Understanding the different types of vaccines and their characteristics is crucial in making informed decisions about vaccination.