Salmonella spp., mycobacteria, and fungi such as Candida and Cryptococcus have been identified in rare instances.Recent research suggests that infectious pathogens play a much smaller role in the pathogenesis than was commonly assumed only a few years ago. Most detected pathogens are very common species that are natural part of the breast fauna and simple detection of their presence is not sufficient to prove a causative role. Furthermore, there are indications that treatment with antibiotics may have minimal impact, and over-all there is insufficient evidence to confirm or refute the effectiveness of antibiotic therapy for treating lactational mastitis. Diagnosis
The diagnosis of mastitis and breast abscess can usually be made based on a physical examination. The doctor will also take into account the signs and symptoms of the condition. However, if the doctor is not sure whether the mass is an abscess or a tumor, a breast ultrasound may be performed. The ultrasound provides a clear image of the breast tissue and may be helpful in distinguishing between simple mastitis and abscess or in diagnosing an abscess deep in the breast. The test consists of placing an ultrasound probe over the breast. In cases of infectious mastitis, cultures may be needed in order to determine what type of organism is causing the infection. Cultures are helpful in deciding the specific type of antibiotics that will be used in curing the disease. These cultures may be taken either from the breast milk or of the material aspirated from an abscess.
An allergic transfusion reaction is when a blood transfusion results in allergic reaction. It is among the most common transfusion reactions to occur. Reported rates depend on the degree of active surveillance versus passing reporting to the blood bank. Overall, they are estimated to complicate up to 3% of all transfusions. The incidence of allergic transfusion reactions is associated with the amount of plasma in the product. More than 90% of these reactions occur during transfusion. Signs and symptoms
Cause
Allergic reactions from blood transfusion may occur from the presence of allergy-causing antigens within the donors blood, or transfusion of antibodies from a donor who has allergies, followed by antigen exposure.An allergic transfusion reaction is a type of transfusion reaction that is defined according to the Center for Disease Control (CDC)  as:

Diagnosis
An allergic transfusion reaction is diagnosed if two or more of the following occur within 4 hours of cessation of transfusion:

A probable diagnosis results if any one of the following occurring within 4 hours of cessation of transfusion:
The UK hemovigilance reporting system (SHOT), has classified allergic reactions in to mild, moderate and severe. Reactions can occur that have features of both allergic and febrile reactions. Mild
A rash, urticaria, or flushing

Moderate
Wheeze (bronchospasm) or angioedema but blood pressure normal and no respiratory compromise. There may or may not be an associated rash or urticaria. Severe
This can be due to:
Severe breathing problems (Bronchospasm, stridor), angioedema, or circulatory problems (e.g. hypotension) which require immediate medical treatment OR admission to hospital OR lengthens the duration of hospital admission.